Regarding large bowel obstruction: Colonic stenting can be used to relieve obstruction, often as a bridge to surgery for malignant obstruction, or for palliation. Hartmann’s procedure can be used in treatment, particularly for sigmoid volvulus or complicated diverticulitis. An erect abdominal X-ray is used to confirm obstruction, not pinpoint the *site*. Barium enema is contraindicated in acute obstruction due to the risk of perforation. Tenderness in the right iliac fossa suggests appendicitis or caecal perforation, not necessarily large bowel obstruction.

The next useful investigation is Colonoscopy. A chronic perianal fistula with intermittent colicky abdominal pain raises the suspicion of Crohn’s disease. Colonoscopy allows for visualization of the colonic mucosa, assessment of inflammation, and biopsy for histological confirmation of Crohn’s. Barium enema is less sensitive for mucosal disease. CRP can indicate inflammation but is non-specific. CT abdomen can show complications like abscesses but is not the first-line investigation for Crohn’s. An X-ray abdomen is not helpful in evaluating fistula or Crohn’s disease.

Regarding investigations for acute severe rectal bleeding: Angiography is used only when there is active bleeding is true. Colonoscopy is useful is true, and often the first-line investigation if the bleeding is not massive. If endoscopy doesn’t reveal a cause, further investigation is needed, but laparoscopy is not necessarily the next step; other options include tagged red blood cell scan or angiography. Radiolabeled red cells scan can be diagnostic, especially for intermittent bleeding. UGIE should be scheduled as an initial investigation is false, as the bleeding is per rectum.

Possible causes of massive bleeding per rectum include Diverticular disease of the colon, Carcinoma of the caecum, and Angiodysplasia of the colon. Duodenal ulcer causes upper GI bleeding. Ileocecal intussusception typically presents with abdominal pain and vomiting, more common in children.

The most appropriate next step in management is Neoadjuvant chemoradiation. For locally advanced rectal cancer, neoadjuvant chemoradiation is the standard of care. It downstages the tumor, increases the chance of sphincter preservation, and reduces local recurrence. Chemotherapy or radiotherapy alone is less effective for local disease control. Anterior resection or abdominoperineal resection are surgical options, but they are typically performed after neoadjuvant therapy in locally advanced cases.

The most appropriate next step in the management is Neoadjuvant chemoradiotherapy. For locally advanced rectal cancer (as indicated by MRI) that is located in the lower rectum, neoadjuvant chemoradiotherapy is the standard of care to downstage the tumor, reduce local recurrence, and improve the chances of sphincter preservation. Anterior resection or abdominoperineal resection would be performed *after* neoadjuvant therapy. Neoadjuvant chemotherapy alone is less effective than chemoradiotherapy for local disease control. Hartmann’s procedure is not typically the first-line treatment for resectable rectal cancer.

The most likely diagnosis is Rectal cancer. The combination of altered bowel habits (loose stools), rectal bleeding, weight loss, and lower back pain strongly suggests rectal cancer. Ulcerative colitis typically presents with more continuous diarrhea and abdominal pain. Solitary rectal ulcer is a localized condition without systemic symptoms like weight loss. Diverticulitis causes abdominal pain, usually in the left lower quadrant, and altered bowel habits, not typically weight loss. Benign rectal polyps usually cause painless bleeding.

The condition is most likely an Intersphincteric abscess. The increasing pain with coughing and straining, and the patient’s inability to tolerate examination, suggest an abscess. An intersphincteric abscess is located between the internal and external anal sphincters, causing significant pain. A fissure in ano causes pain during and after defecation. Grade II hemorrhoids are usually painless. A perianal hematoma causes acute, localized pain at the anal verge.

Painful perianal conditions include: Acute fissure in ano, Perianal hematoma, and Perianal abscess. Carcinoma of the rectum is usually painless initially. Uncomplicated fistula in ano is not typically associated with severe pain.

The most appropriate investigation is Contrast CT abdomen. The patient’s presentation (left lower quadrant pain, fever, tenderness, guarding, and leukocytosis) strongly suggests acute diverticulitis. A contrast CT scan is the best imaging modality to confirm the diagnosis, assess the severity of the diverticulitis, and identify any complications such as abscess formation or perforation. Barium enema and colonoscopy are contraindicated in the acute phase. A supine abdominal X-ray can show signs of obstruction or perforation but is not specific for diverticulitis. Diagnostic laparoscopy is invasive and not the first-line investigation.

The most likely diagnosis is Perianal hematoma. The acute onset of a painful lump at the anal verge after straining is characteristic of a perianal hematoma, which is a collection of blood outside the anal canal. An acute anal fissure would cause severe pain during and after defecation, with blood on the stool, not a lump. A fistula-in-ano presents with a chronic discharging sinus. A perianal abscess is more painful and may be associated with fever. Second-degree hemorrhoids are internal and would not present as an acute, painful external lump.

The most likely site of pathology is the Ileum. Chronic diarrhea, macrocytic anemia, numbness of extremities, and fatigue point towards malabsorption. The ileum is the primary site of vitamin B12 absorption, and its dysfunction (e.g., in Crohn’s disease) can lead to B12 deficiency, causing macrocytic anemia and neurological symptoms. The ascending colon is more associated with iron deficiency anemia. The jejunum is involved in the absorption of most nutrients, and its dysfunction would cause a broader range of deficiencies. The stomach is related to B12 absorption, but intrinsic factor is produced here, the absorption happens in the terminal ileum. Transverse colon mainly absorbs water and electrolytes.

The most appropriate initial radiological investigation for suspected closed-loop large bowel obstruction is X-Ray abdomen supine. A plain abdominal X-ray can quickly and easily show dilated loops of bowel and air-fluid levels, which are suggestive of obstruction. In closed-loop obstruction, there’s a risk of rapid deterioration, so a quick initial assessment is crucial. CT abdomen is more detailed but takes longer. Gastrografin enema is contraindicated in suspected obstruction. Barium meal and follow-through is for small bowel evaluation. MRI is not used for acute obstruction.

The most likely diagnosis is Haemorrhoids. Painless, fresh PR bleeding after defecation, especially with a history of constipation and a normal digital rectal exam, strongly suggests internal hemorrhoids. An acute anal fissure would cause significant pain. Rectal carcinoma usually presents with altered bowel habits and may be painful. Diverticulosis is typically painless and causes more massive bleeding. Ulcerative colitis causes bloody diarrhea, not isolated bleeding after defecation.

Causes of massive painless bleeding include Meckel’s diverticulum (especially in younger patients) and Angiodysplasia (more common in older patients). Diverticulitis typically presents with pain, though bleeding can occur. Hemorrhoids usually cause mild to moderate bleeding, not massive bleeding.

The next step in the management is Conservative management with IV antibiotics. For a patient with a pericolic diverticular abscess, especially if it’s large, initial management involves IV antibiotics and bowel rest. If the patient doesn’t improve or if there are signs of generalized peritonitis, surgical intervention (drainage or resection) may be needed. Emergency laparotomy is not the first step. Laparoscopic or USS-guided drainage may be considered later if conservative management fails.

Following an anterior resection: Hypokalemia can lead to paralytic ileus. If develops fever on Day 1, it could be due to lung atelectasis. Fever on day 5 is more typical of anastomotic leak. Patients are kept NPO until bowel function returns. The risk of DVT is similar to that of right hemicolectomy.

The most likely cause is Adhesions. The history of previous laparotomy for bowel perforation is a strong risk factor for adhesive small bowel obstruction. Sudden onset of bilious vomiting and abdominal distension are typical. Carcinoma of the colon would have a more gradual onset. Gallstone ileus is less likely without typical gallstone symptoms. Inguinal hernia would have a visible or palpable hernia. Paralytic ileus is usually post-operative or associated with medical conditions.

Causes of massive fresh bleeding per rectum include Angiodysplasia of the colon and Diverticular disease of the colon. These are common causes of significant lower GI bleeding, especially in older patients. Mallory-Weiss syndrome causes upper GI bleeding. Meckel’s diverticulum can cause bleeding, but it’s more common in children. Radiation proctitis typically causes chronic, not massive, bleeding.

The most important factor in preventing surgical site infections in colonic surgery is Prophylactic antibiotic use. Mechanical bowel preparation is also important, but prophylactic antibiotics are crucial due to the high bacterial load in the colon. Pre-operative carbohydrate loading is for enhanced recovery, not directly for infection prevention. Preoperative nutrient supplementation is for malnourished patients. Shaving the abdomen increases infection risk.

Extra-intestinal manifestations of inflammatory bowel disease (IBD) include Ankylosing spondylitis, Large joint arthritis, Sclerosing cholangitis, and Uveitis. Erythema multiforme is not typically associated with IBD.

True statements regarding fistula in ano include: Seton drainage gives symptomatic relief and Gel injection is a method of treatment. Fistulectomy in Crohn’s disease is contraindicated. Low anal fistulae *can* cause damage to lower anal sphincters. They commonly present with pain and discharge, not primarily bleeding.

The most appropriate next step of management is a Fluid trial with normal saline. The patient shows signs of oliguria, tachycardia, and mild hypotension, suggesting hypovolemia. A fluid challenge with crystalloid (normal saline) is the first step to improve renal perfusion and urine output. Blood transfusion is not indicated as the patient is not pale. Inotropes are used if hypotension persists despite adequate fluid resuscitation. Immediate relaparotomy is not indicated. Intravenous frusemide is contraindicated in hypovolemia.

The most likely diagnosis is Hemorrhoid. Painless fresh rectal bleeding, especially with a history of constipation, is most commonly due to internal hemorrhoids. An acute anal fissure is typically associated with significant pain during and after defecation. Sigmoid diverticulitis and ulcerative colitis usually present with abdominal pain and altered bowel habits. Rectal cancer is less likely in this age group and often has other symptoms.

The most probable finding on proctoscopy is Hemorrhoids. Painless fresh per rectal bleeding in a young patient with a normal DRE is most commonly due to internal hemorrhoids. Rectal cancer is less likely in this age group and usually has other symptoms. Sigmoidal diverticulitis typically presents with left lower quadrant pain. Ulcerative colitis would likely have a history of diarrhea and mucus discharge. Anal fissure is very painful.

The most probable cause is Perforated peptic ulcer. Though the patient had anterior resection, the free gas under the diaphragm on erect chest X-ray strongly suggests a perforated viscus, most likely a perforated peptic ulcer. Painless abdominal distention and absent bowel sounds can be seen in both, but free gas is diagnostic of perforation. Anastomotic leakage would present with more signs of sepsis. Bowel ischemia would have severe pain. Internal bowel herniation would not typically cause free gas. Paralytic ileus does not cause free gas.

The investigation to confirm the diagnosis of intussusception is USS scan. The classic presentation of a 7-month-old baby with abdominal pain, distension, and red currant jelly stool strongly suggests intussusception. Ultrasound is the initial imaging modality of choice for its high sensitivity and ability to visualize the ‘target’ or ‘doughnut’ sign. Barium enema can be both diagnostic and therapeutic, but ultrasound is preferred initially. Colonoscopy and CT abdomen are not the first-line investigations. X-ray abdomen may show signs of obstruction but is not specific for intussusception.

The most probable diagnosis is Gallstone ileus. The combination of colicky abdominal pain, a history of dyspepsia related to heavy meals, dilated small bowel loops, and aerobilia on X-ray is classic for gallstone ileus. The gallstone erodes through the gallbladder wall into the duodenum, causing a small bowel obstruction. Adhesive intestinal obstruction would not typically show aerobilia. Sigmoid volvulus presents with large bowel obstruction. Emphysematous cholecystitis causes right upper quadrant pain and gas in the gallbladder wall. A perforated peptic ulcer would present with more acute and severe pain and signs of peritonitis.

Regarding anal fistula: In Crohn’s, recurrent and fistulae present. Most need surgical treatment. Seton drainage gives symptomatic relief. In Sri Lanka, the common cause is not TB. Low anal fistulae, if treated improperly, can cause damage to lower anal sphincters. Gel injection is a method of treatment.

Regarding colonic carcinoma: Rectosigmoid CA can be managed with APR (Abdominoperineal resection) if it is low rectal cancer. Stenosis is more common in left-sided carcinoma. The commonest site of metastases is the liver. CEA is not confirmatory. Screening high-risk people is done with colonoscopy.

Complications of diverticular disease include: Colonic strictures, Colovesical fistula, Massive lower gastrointestinal bleeding, and Perforation. Colonic cancer is not a direct complication of diverticular disease.

The most appropriate next step in management is Neoadjuvant chemo-radiotherapy. For locally advanced rectal cancer, neoadjuvant chemoradiotherapy is the standard of care. It downstages the tumor, increases the chance of sphincter preservation, and reduces local recurrence. APR (abdominoperineal resection) and AR (anterior resection) are surgical options, but they are typically performed after neoadjuvant therapy in locally advanced cases. A stent may be used for palliation in obstructing tumors, not as primary treatment. Neoadjuvant chemotherapy alone is less effective than chemoradiotherapy for local disease control.

Regarding surgery on the colon and rectum: Hartmann procedure is the safest surgery for perforated sigmoid colon. Total mesorectal excision reduces the recurrence after anterior abdominal resection. Anastomotic leak is more common after low anterior resection. An end colostomy can be reversible. An ileal pouch improves quality of life after total proctocolectomy.

Pre-malignant lesions of the colon include Ulcerative colitis, Peutz Jegher syndrome, and Serrated adenoma. Crohn’s disease increases the risk of colon cancer, but is not considered a pre-malignant lesion. Diverticular disease is not associated with an increased risk of colon cancer.

The most likely diagnosis is Diverticular mass. The presentation of lower abdominal pain, fever, vomiting, a history of altered bowel habits, and a left iliac fossa mass suggests sigmoid diverticulitis with a possible abscess. The recurrent episodes are also typical of diverticular disease. Acute pyelonephritis would have urinary symptoms. Fulminant ulcerative colitis presents with bloody diarrhea and systemic toxicity. A left tubo-ovarian mass wouldn’t typically cause vomiting or altered bowel habits. Locally advanced carcinoma of the sigmoid colon is less likely to have such an acute presentation.

The most probable diagnosis is Meckel’s diverticulum. In a young patient presenting with recurrent, heavy, painless rectal bleeding, Meckel’s diverticulum containing ectopic gastric mucosa is a common cause. The gastric mucosa can ulcerate and bleed. Angiodysplasia is more common in older patients. Ulcerative colitis typically presents with diarrhea, abdominal pain, and mucus in the stool. Diverticular disease is rare in this age group. Iliocolic intussusception usually presents with acute abdominal pain and a palpable mass in infants.

Regarding familial adenomatous polyposis (FAP): It is diagnosed when there are more than 100 polyps in the colon during colonoscopy. It is common to have extraintestinal manifestations (e.g., desmoid tumors). 100% of affected individuals have a positive family history, but it may not be apparent due to new mutations. Total proctocolectomy is the *prophylactic* treatment. Screening should begin in adolescence, around 10-12 years of age, not 25.

The best fluid therapy for the next 24 hours is IV 0.9% NaCl with KCl 1500ml. The child presents with signs of dehydration (thirst, dry mouth) and adhesive intestinal obstruction. The low serum chloride indicates a need for chloride replacement, which 0.9% NaCl provides. The maintenance fluid rate for a 20kg child is approximately 60ml/hr (4ml/kg/hr for the second 10kg). 1500ml over 24 hours is approximately 62.5ml/hr. Potassium chloride should be added to address the potassium loss. 0.9% NaCl + 5% dextrose adds unnecessary glucose. 0.45% NaCl is hypotonic and less ideal for initial resuscitation. A bolus may be needed in addition to this 24 hour replacement.

The best investigation to assess loco-regional spread of distal rectal carcinoma is MRI and/or EUS (Endoscopic Ultrasound). MRI pelvis provides detailed information about tumor depth, nodal involvement, and involvement of adjacent structures. EUS is also excellent for T and N staging, especially for distal rectal cancers. CECT is less accurate for local staging. PET is used for distant metastases. USS is not the primary modality for rectal cancer staging.

Regarding presentations of colorectal carcinoma: Colonic obstruction is common in left side, sigmoid carcinoma present with PR bleeding, carcinoma in transverse colon present as emergency. Right sided colonic cancers tend to present with iron deficiency anemia. Colonic carcinoma does not typically cause fecal incontinence unless it is very low rectal cancer.

The next step in the management is Sigmoidoscopy. The patient’s age, history of chronic constipation, and X-ray findings suggest sigmoid volvulus. Sigmoidoscopy can be both diagnostic and therapeutic, often allowing for decompression of the volvulus. If sigmoidoscopy is unsuccessful, laparotomy may be required. Barium enema and hydrostatic reduction are contraindicated in suspected volvulus. CT can be used for diagnosis but sigmoidoscopy is preferred as the initial step.

Regarding the blood supply of the rectum and colon: The anal canal is a site of porto-systemic anastomosis. Superior sigmoidal veins drain to inferior mesenteric vein. Most of the venous drainage from the rectum is to the systemic circulation. The rectosigmoid junction is supplied by the inferior mesenteric artery. The hemorrhoidal artery is a branch of the internal iliac artery, not the inferior mesenteric artery.

The most likely cause is Anastomotic leakage. The combination of abdominal pain, distension, tachycardia, and tachypnea on post-op day 5 following anterior resection is highly suggestive of anastomotic leakage. The lower abdominal pain is typical. Intestinal obstruction is less likely to present this early with these vital sign changes. Secondary hemorrhage would present with a drop in blood pressure and pallor. Pneumonia would have more respiratory symptoms. UTI is less likely to cause this acute abdominal picture.

Regarding ulcerative colitis: Crypt abscess is characteristic. It is more common in the left colon. Proctocolectomy improves extraintestinal manifestations. It is less common in smokers. Ulcerative colitis involves the mucosa and submucosa, not transmural.

Regarding hemorrhoids: Straining while defecation is a predisposing factor. Thrombosed hemorrhoids can be managed conservatively (initially). They are prolapsed anal cushions. Hemorrhoids are not premalignant.

The most likely diagnosis is Paralytic ileus. The history of acute gastroenteritis followed by abdominal distention, pain, absent bowel sounds, and electrolyte imbalance (hypokalemia) is characteristic of paralytic ileus. Acute intestinal obstruction typically presents with vomiting and high-pitched bowel sounds initially. Toxic megacolon is associated with severe colitis and systemic toxicity. Pyloric stenosis presents with early vomiting. Acute intestinal obstruction is characterized by mechanical blockage, which is not the case here.

Treatment is facilitated by a defunctioning stoma for High fistula-in-ano (to divert stool and promote healing) and Perineal necrotising fasciitis (to divert stool and reduce contamination). A defunctioning stoma is less relevant for a 3rd-degree vaginal tear, prolapsed thrombosed hemorrhoids, or a grade 4 sacral pressure sore.

Painful perianal conditions include Acute fissure-in-ano, Perianal abscess, and Perianal hematoma. Second-degree hemorrhoids are typically associated with painless bleeding. Anal warts are usually painless.

Regarding drains: Drains can be used to diagnose anastomotic leak (by noting the characteristics of the fluid). Drains can be used to diagnose bleeding. Drains do not impair anastomotic healing. Drains may increase the risk of infection. Drains should be removed when drainage is minimal.

The most appropriate management option is Colonic stenting. For an elderly patient with comorbidities (hypertension and diabetes) presenting with an obstructing rectosigmoid carcinoma, colonic stenting is often the best initial approach. It relieves the obstruction, allowing for bowel decompression and optimization of the patient’s condition before definitive surgery. This can reduce the risk of complications. Elective anterior resection after optimizing is a definitive treatment but not the initial step in an obstructed patient. Hartmann’s procedure is a surgical option, but stenting is less invasive initially. Loop colectomy and tumor resection is also a surgical option but stenting is preferred. Image-guided drainage is not typically used in this scenario.

In small intestinal obstruction: Continuous abdominal pain indicates strangulation, a surgical emergency. It is commonly caused by post-op adhesions. Passage of flatus does not exclude complete obstruction. Abdominal distension is a late feature. Elevated serum amylase is more associated with pancreatic disease, but can be mildly elevated in SBO.

The most likely diagnosis is Ca of rectum. The combination of altered bowel habits (loose stools), obstructive symptoms (incomplete evacuation), and rectal bleeding strongly suggests rectal cancer, especially in a 70-year-old man. Sigmoid cancer can cause similar symptoms, but rectal cancer often presents earlier with tenesmus. Solitary rectal ulcer typically causes more localized rectal discomfort and bleeding. Caecum cancer usually presents with anemia or a right-sided mass. Ulcerative colitis would have a longer history and more diffuse colonic involvement.

Conditions presenting with recurrent sinuses/fistulae include Actinomycosis, Crohn’s disease, and Hydradenitis suppurativa. Anal fissures typically do not cause recurrent fistulae. Tuberculosis can cause fistulae, but it’s less common in developed countries.

Excess abdominal expansion due to pneumoperitoneum: Causes acidosis, Is a cause of bowel ischemia, and Tachycardia. Pneumoperitoneum can lead to respiratory compromise, causing acidosis. It can also increase intra-abdominal pressure, leading to bowel ischemia. Tachycardia is a common response to pain and hypovolemia. Pneumoperitoneum typically *increases*, not reduces, the end-tidal volume of CO2.

The most likely diagnosis is anastomotic leak. The next investigation to come to a diagnosis is contrast enhanced CT. The patient’s presentation (abdominal pain, distension, tachycardia, hypotension, tachypnea, and abdominal tenderness) strongly suggests a post-operative complication such as anastomotic leak. A contrast-enhanced CT scan of the abdomen and pelvis is the most sensitive and specific imaging modality for diagnosing an anastomotic leak. It can show extraluminal contrast, fluid collections, and other signs of leakage. Colonoscopy is contraindicated in suspected anastomotic leak. Erect chest X-ray is used to look for free air in cases of perforation, which is less likely here. Laparoscopy may be used for treatment but not for initial diagnosis. Peritoneal tap is less specific and invasive than a CT scan.

For a 45-year-old male with rectal cancer, appropriate management considerations include: Neoadjuvant chemoradiotherapy, particularly for locally advanced rectal cancer to downstage the tumor and improve surgical outcomes, and Total mesorectal excision, which is the standard surgical approach for rectal cancer. Anterior resection is a surgical option, but its suitability depends on the tumor’s location (it’s less suitable for very low rectal cancers). Abdominoperineal resection is reserved for low rectal cancers involving the anal sphincter. Palliative chemotherapy is used for metastatic disease, not as a primary treatment for localized rectal cancer.

The best diagnostic test to diagnose local invasion of rectal carcinoma is EUS (Endoscopic Ultrasound). EUS provides the most accurate assessment of the depth of tumor invasion (T staging) and lymph node involvement in rectal cancer, which is crucial for treatment planning. CT and MRI are used for staging but are less accurate for local invasion. Diagnostic laparotomy is invasive and not used for staging. PET is used for distant metastases.

Regarding acute anal fissure: Lateral internal sphincterotomy is performed to treat intractable fissures. Local application of nitroglycerine gel is used in treatment. Most are located at the 6 o’clock position of the anal canal. Diagnosis is clinical, proctoscopy is painful and not first line. Most acute fissures heal with conservative management.

The most probable diagnosis is CA of rectum. The symptoms described (loose stools, urgency, incomplete evacuation, tenesmus, and rectal bleeding) are highly suggestive of rectal cancer. These symptoms arise from the tumor’s location in the rectum. While ulcerative colitis can present with similar symptoms, the patient’s age (70 years) makes rectal cancer more likely, and the examination findings (normal except for blood) are less typical of extensive colitis. CA of the cecum usually presents with iron deficiency anemia or a right-sided mass. Diverticular disease typically causes left lower quadrant pain and altered bowel habits, not usually tenesmus or a sense of incomplete evacuation. Solitary rectal ulcer, while causing bleeding and tenesmus, doesn’t usually present with such a long history of loose stools.

The most appropriate management is Defunctioning colostomy and palliative chemotherapy. The patient has metastatic colorectal cancer (liver metastasis). The primary goal is palliation. A defunctioning colostomy can relieve the obstructive symptoms from the rectosigmoid tumor. Palliative chemotherapy is indicated for systemic disease. Resection of the primary tumor (Hartmann’s or anterior resection) and liver resection are not indicated in this setting of metastatic disease. Stenting alone does not address the systemic disease.

For a 45-year-old with ulcerative colitis exacerbation: Can be managed as outpatient or Responds to steroid therapy. Most exacerbations can be managed with outpatient oral steroids. Urgent laparotomy is for severe or fulminant colitis. Immediate colonoscopy is contraindicated in severe colitis. Sulfasalazine can be used for maintenance, but steroids are needed for acute exacerbations.

Following a right hemicolectomy for colon cancer with lymph node involvement, the patient requires Adjuvant chemotherapy. This is stage III colon cancer, and adjuvant chemotherapy reduces the risk of recurrence. Colonoscopy follow-up is essential for surveillance. Family screening is important due to the potential for hereditary syndromes. Adjuvant radiotherapy is not typically used for colon cancer. Expectant management is incorrect.

The most likely place of obstruction is the Rectosigmoid. The history of abdominal distention, vomiting, absolute constipation, and a past history of abdominal pain with painful defecation suggests a distal large bowel obstruction. Rectosigmoid is a common site for obstructing colorectal cancer or strictures. Hepatic and splenic flexures are less common sites for obstruction. Mid-jejunum obstruction would present earlier with vomiting and less with constipation. Caecum is more associated with right-sided obstruction.

The most likely diagnosis is Villous Adenoma of Rectum. Episodic painless bleeding and mucus discharge, with normal appetite and no weight loss, are characteristic of a villous adenoma. These tumors can secrete large amounts of mucus. Chronic fistula typically presents with persistent discharge and pain. Sigmoid diverticulosis usually causes painless bleeding, but mucus discharge is less common. First-degree rectal prolapse might cause bleeding but less mucus. Rectal prolapse typically presents with a palpable protrusion.

Regarding acute anal fissures: They are commonly seen at the posterior midline. Topical calcium channel blockers are therapeutic. Flexible sigmoidoscopy can be done. They are *not* typically associated with sentinel piles (which are associated with chronic fissures). Surgical option for *chronic* fissures is internal sphincterotomy.

Regarding familial adenomatous polyposis (FAP): By adolescence, patients with FAP manifest with multiple polyps. FAP is associated with desmoid tumors. FAP is managed by total colectomy, often with ileal pouch-anal anastomosis, not APR in all cases. FAP is equally seen in males and females.

The best investigation is Flexible sigmoidoscopy. Given the patient’s age, per rectal bleeding, and incomplete evacuation, colorectal cancer is a significant concern. Flexible sigmoidoscopy allows direct visualization of the rectum and sigmoid colon, where most colorectal cancers occur. If sigmoidoscopy is normal and symptoms persist, a full colonoscopy would be needed. Barium swallow and capsule endoscopy are for upper GI. CT is for staging. Stool occult blood is a screening test, not diagnostic.

Possible diagnoses include: Rectal carcinoma, Ulcerative colitis, and Villous adenoma of the rectum. These symptoms (rectal bleeding, mucus, incomplete evacuation) suggest a rectal or distal colonic lesion. An anal fissure causes pain, not typically mucus or incomplete evacuation. Solitary rectal ulcer is more associated with straining and rectal pain.

The most probable cause is Perianal hematoma. Sudden onset of severe perianal pain following straining, with a tender, firm lump, is characteristic of a perianal hematoma. The location at the 4 o’clock position is consistent. Anal fissure causes severe pain during and immediately after defecation, and there may be blood on the stool, but not a lump. Perianal abscess is associated with more diffuse swelling and systemic symptoms. Perianal fistula presents with chronic discharge. Prolapsed thrombosed hemorrhoids are usually internal and cause more diffuse swelling.

The initial management of severe pain and fresh PR bleeding is Topical GTN (glyceryl trinitrate). This presentation is highly suggestive of an acute anal fissure. GTN promotes vasodilation, increasing blood flow to the area and aiding healing, while also reducing anal sphincter spasm and pain. Lateral sphincterotomy is a surgical treatment for chronic or intractable fissures, not the initial management. Botox injections are also used for chronic fissures. Manual anal dilatation is no longer recommended. Colonoscopy is not indicated for the initial management of a suspected acute anal fissure.

The main objective of neoadjuvant chemotherapy in this scenario is to Reduce the local recurrence. For rectal cancer, neoadjuvant chemoradiotherapy (often used interchangeably) is given to downstage the tumor and reduce the risk of local recurrence. It may increase survival, but that’s a secondary aim. It does not directly reduce liver metastasis or metachronous tumors.

Fresh painful PR bleeding occurs in Anal fissure and Thrombosed hemorrhoids. Rectal polyps and angiodysplasia typically cause painless bleeding. Perianal abscess is associated with significant pain, but the bleeding is usually less prominent and associated with purulent discharge.

Regarding small intestinal obstruction: Persistent severe pain indicates strangulation. The commonest cause is adhesions. Bowel opening does not exclude complete obstruction. Elevated serum amylase does not exclude obstruction. The level of obstruction is assessed by a supine and erect abdominal X-ray.

The most appropriate curative management for squamous cell carcinoma of the anus is Chemo-radiotherapy. This is the standard of care for anal cancer, as it offers better sphincter preservation and equivalent survival compared to surgery. Abdominoperineal resection is reserved for persistent or recurrent disease after chemoradiotherapy. Anterior resection is for rectal cancer. Primary radiation therapy alone is less effective than chemoradiotherapy. Transanal excision is for early rectal cancer, not anal cancer.

The most likely diagnosis is Ischemic colitis. The patient’s age, atrial fibrillation, sudden onset of abdominal pain, and rectal bleeding are classic signs of ischemic colitis. The elevated white blood cell count supports this. Angiodysplasia usually presents with painless bleeding. Carcinoma of the colon typically presents with more gradual changes in bowel habits. Diverticulitis causes localized pain and fever. Ulcerative colitis presents with chronic diarrhea and bloody stools.

The most appropriate management is Sigmoid decompression with flatus tube. The ‘coffee bean’ sign on abdominal X-ray is classic for sigmoid volvulus. In the absence of peritonitis, initial management involves endoscopic decompression. Emergency laparotomy is indicated if there is evidence of strangulation, perforation, or if endoscopic decompression fails. Monitoring for 48 hours is not appropriate in the presence of absolute constipation and distension. Phosphate enema is used for fecal impaction, not volvulus. Sigmoid colectomy is the definitive treatment but is usually performed electively after successful decompression.

The features that favor Crohn’s disease over ulcerative colitis include Anal fissures and Recurrent abdominal pain. While both can cause altered bowel habits, blood, and mucus, Crohn’s is more associated with penetrating disease (fissures) and abdominal pain. Episodes of intestinal obstruction are more common in Crohn’s. Polyarthralgia can occur in both. Recurrent UTIs are not a typical distinguishing feature.

The next step of management is Neoadjuvant chemoradiotherapy. For locally advanced rectal cancer, neoadjuvant chemoradiotherapy is the standard of care. It downstages the tumor, increases the chance of sphincter preservation, and reduces local recurrence. Abdominoperineal resection and anterior resection are surgical options, but they are typically performed after neoadjuvant therapy in locally advanced cases.

The most likely diagnosis is acute ischemic colitis. The patient’s age, history of atrial fibrillation (a risk factor for thromboembolism), acute onset of severe generalized abdominal pain with few abdominal signs, and elevated inflammatory markers and lactate levels are highly suggestive of mesenteric ischemia. While perforated duodenal ulcer can cause severe abdominal pain, it typically presents with more pronounced peritonitis. Acute cholangitis presents with right upper quadrant pain, fever, and jaundice. Acute pancreatitis presents with severe epigastric pain. Diverticular disease, while common in this age group, usually causes left lower quadrant pain and altered bowel habits.

The next step in the management is Flexible sigmoidoscopy. In a young patient with painless rectal bleeding and a normal DRE, flexible sigmoidoscopy is appropriate to evaluate for internal hemorrhoids, polyps, or other mucosal abnormalities. While lifestyle modification is always important, further investigation is needed. Band ligation and hemorrhoidectomy are treatments, not initial investigations. Sclerotherapy is also a treatment.

The most likely cause for this presentation is Adhesions. A history of previous abdominal surgery (appendectomy) is the most common cause of small bowel obstruction due to adhesions. The dilated small bowel on X-ray supports this. Diverticular disease primarily affects the colon. Inguinal hernia can cause obstruction, but the X-ray findings are less typical. Intussusception is rare in adults. Splenic flexure carcinoma would cause large bowel obstruction.

The most likely diagnosis is Anal fissure. The combination of painful defecation and blood streaked on stools in a young, pregnant woman strongly suggests an anal fissure. Pregnancy can predispose to constipation and anal fissures. Fistula in ano typically presents with persistent discharge and recurrent perianal swelling. Rectal prolapse involves protrusion of the rectal mucosa. First-degree hemorrhoids are usually painless. Angiodysplasia is rare in this age group and during pregnancy.

The most appropriate next step of management is Crystalloid bolus and Blood transfusion. The patient presents with signs of hemodynamic instability (hypotension, tachycardia) due to massive PR bleeding. Initial management focuses on resuscitation with crystalloid solutions and blood transfusion to restore circulating volume and oxygen-carrying capacity. Colonoscopy and CT angiography are important for identifying the source of bleeding, but not before initial resuscitation. Withholding clopidogrel is important but secondary to immediate stabilization.

The most probable cause is Hypovolaemia. In the immediate postoperative period following major surgery like anterior resection, oliguria, tachycardia, and hypotension are most commonly due to hypovolemia from blood loss or inadequate fluid replacement. Sepsis is less likely this early. Myocardial infarction would present with chest pain and ECG changes. Pulmonary embolism may cause tachycardia and hypotension but is less common on post-op day 1. Unresolved pain alone is unlikely to cause this degree of hemodynamic instability.

In ulcerative colitis, Hypoalbuminaemia is indicative of severe disease. Granuloma formation is characteristic of Crohn’s disease, not ulcerative colitis.