A 35-year-old woman presents to her outpatient clinic with a 4-week history of intermittent bright red blood per rectum, accompanied by a feeling of incomplete evacuation. She reports having loose, blood-streaked bowel movements three to four times daily. She denies significant abdominal pain, fever, or weight loss. Her vital signs are stable, and the remainder of the physical examination, including a digital rectal exam, is unremarkable, with only mild tenderness in the left lower quadrant on deep palpation. Initial laboratory studies are obtained. A colonoscopy was performed, revealing diffuse and symmetric inflammatory mucosal changes characterized by erythema and friability, with an absent mucosal vascular pattern extending from the rectum to the mid-sigmoid colon. Biopsy specimens obtained from these areas show chronic colitis. Results of testing for Clostridioides difficile toxin were negative. Considering these findings, what is the most probable diagnosis and the cornerstone of its initial management?

A 48-year-old woman presents to her gastroenterology outpatient clinic complaining of persistent fatigue and occasional mild pruritus over the last 6 months. She denies any abdominal pain, vomiting, fever, or significant weight loss. Her past medical history is significant for ulcerative colitis, diagnosed 5 years ago, which is currently well-controlled with oral 5-aminosalicylic acid and periodic steroid enemas. On physical examination, her temperature is 37.0 C (98.6 F), blood pressure is 132/88 mm Hg, pulse is 72/min, and respirations are 16/min. Abdominal examination reveals mild tenderness in the left lower quadrant. There is no palpable hepatomegaly or splenomegaly, and no signs of jaundice or scleral icterus. Considering her long-standing history of inflammatory bowel disease, her current symptoms, and these laboratory findings, what is the most likely diagnosis and the most appropriate initial diagnostic imaging study to confirm it?

A 30-year-old man with a known history of ulcerative colitis presents to the Emergency Department with a 3-day history of worsening bloody diarrhea, now with 8-10 bowel movements per day, accompanied by severe cramping lower abdominal pain and generalized malaise. He reports low-grade fever and increased urgency. He has been on mesalamine 1.2 g orally twice daily, but his symptoms have recently escalated. On physical examination, his vital signs include a temperature of 38.2°C, heart rate 105 bpm, blood pressure 110/70 mmHg, and respiratory rate 18 breaths/min. Abdominal examination reveals diffuse tenderness, more pronounced in the left lower quadrant, with mild guarding. Bowel sounds are diminished. Rectal examination confirms bright red blood. A recent colonoscopy, performed two months prior for disease activity assessment, showed continuous inflammation extending from the rectum to the descending colon, with moderate to severe friability and ulcerations. Biopsy specimens demonstrated chronic active inflammation with crypt architectural distortion and crypt abscesses. Stool studies for Clostridioides difficile toxin are negative. Considering the patient's current presentation and known diagnosis, what is the most appropriate initial medical management, and what serious complication should always be monitored for in such cases?

A 45-year-old male with a known history of ulcerative colitis presents to the emergency department after several days of increasing abdominal pain, frequent bloody bowel movements, and generalized weakness. His symptoms began subtly over the past week with loose, bloody stools, but in the last 24 hours, he has developed severe, constant abdominal pain, high-grade fevers, and chills. He reports decreased urine output and lightheadedness upon standing. His current medications include mesalamine, which he admits to not taking regularly in recent months. On examination, he appears acutely ill and lethargic. His temperature is 39.5°C, pulse is 130/min, blood pressure is 85/50 mmHg, and respiratory rate is 22/min. His oral mucosa are severely dry. Abdominal examination reveals marked distension, diffuse tenderness to palpation, and quiet bowel sounds. There is no overt rebound tenderness or guarding. Peripheral pulses are weak. Laboratory tests are drawn. Considering his acute presentation, what is the most critical initial diagnostic imaging study, and what immediate medical intervention should be initiated concurrently?

A 48-year-old male with a long-standing history of ulcerative colitis, managed on mesalamine, is admitted to the general medical ward from the emergency department presenting with a three-day history of escalating symptoms including increased frequency of bloody, loose stools (up to 15-20 times daily), severe abdominal pain, and subjective fevers. On examination, he appears acutely ill and lethargic. Vital signs reveal a temperature of 39.4°C, heart rate of 110 bpm, blood pressure of 105/70 mmHg, respiratory rate of 22 breaths/min, and oxygen saturation of 96% on room air. His abdomen is significantly distended with an abdominal circumference of 102 cm, diffusely tender to palpation, and exhibits absent bowel sounds. Mild rebound tenderness is noted in the left lower quadrant. Abdominal radiographs show a markedly dilated colon, particularly in the transverse and descending segments, with a diameter of approximately 9 cm at the transverse colon. A subsequent computed tomography (CT) scan confirms extensive colonic dilation without evidence of free air or explicit perforation. What is the most likely diagnosis and the immediate critical intervention required for this patient, considering potential life-threatening complications?

A 38-year-old woman presents to her primary care physician with a 3-day history of escalating abdominal pain and frequent bloody bowel movements, occurring up to 8-10 times daily. She reports a long-standing history of intermittent abdominal cramping and occasional loose stools, previously attributed to irritable bowel syndrome. She also has a history of allergic rhinitis and migraines, managed with loratadine and occasional sumatriptan. Her current episode began with diffuse cramping pain, which has now localized to the left lower quadrant and is accompanied by tenesmus and significant fatigue. She denies recent travel, antibiotic use, or consumption of raw seafood. On examination, she appears pale and acutely distressed. Her temperature is 37.9°C, blood pressure is 98/65 mmHg, pulse is 118/min, respirations are 16/min, and oxygen saturation is 97% on room air. Abdominal palpation reveals diffuse tenderness, more pronounced with guarding and rebound in the left lower quadrant. Bowel sounds are diminished. Digital rectal examination confirms grossly bloody stool. Given her clinical presentation, she is immediately transferred to the emergency department. Initial investigations are performed, including an abdominal radiograph which demonstrates an apparent 'lead pipe' appearance of the colon, and a subsequent urgent flexible sigmoidoscopy reveals diffuse mucosal inflammation with friability and ulcerations extending from the rectum proximally. Biopsies taken show marked crypt architectural distortion, crypt abscesses, and an abundant lymphoplasmacytic infiltrate in the lamina propria. What is the most likely diagnosis, and what is the most appropriate initial management strategy for this patient?

A 38-year-old female with a known history of severe ulcerative colitis, previously managed with oral 5-aminosalicylic acid, is admitted to the gastroenterology ward for a severe flare-up. Over the past 24 hours, her condition has acutely worsened. She reports persistent severe abdominal pain, worsening bloody diarrhea (now 8-10 episodes per day), and has developed profound nausea with intermittent vomiting. On physical examination, she appears acutely ill and distressed. Her abdomen is distended, diffusely tender to palpation with rebound tenderness, and notably tympanitic on percussion. Bowel sounds are diminished. Her vital signs are: Temperature 38.8 °C, Heart Rate 115 bpm, Blood Pressure 105/65 mmHg, Respiratory Rate 22 bpm, and Oxygen Saturation 98% on room air. An urgent plain abdominal radiograph shows marked colonic dilation, particularly of the transverse colon, measuring 7.5 cm. Considering these findings, what is the most appropriate initial management strategy, and what critical complication must be actively monitored for?

A 30-year-old man presents to the gastroenterology clinic for a follow-up after experiencing a 3-week flare of chronic symptoms. He reports worsening abdominal pain, persistent bloody diarrhea occurring 6-8 times per day, significant nocturnal bowel movements, and an additional 4 kg unintentional weight loss over the past month. He also notes recent joint pain and intermittent blurry vision. His past medical history is notable for mild ulcerative colitis diagnosed 5 years ago, which was previously managed with oral mesalamine, but his compliance has been inconsistent. His mother has a history of primary sclerosing cholangitis. On physical examination, his temperature is 37.80C (100.00F), blood pressure is 105/70 mmHg, pulse is 95/min, and oxygen saturation is 98% on room air. Abdominal examination reveals diffuse tenderness to palpation, particularly in the left lower quadrant, but no rebound or guarding. Digital rectal examination confirms visible blood and mucus. A recent colonoscopy performed during this flare showed extensive colonic inflammation extending from the rectum proximally. Considering his presentation, what is the most appropriate long-term management strategy, and what specific endoscopic finding would confirm the underlying diagnosis?

A 28-year-old man presents to the clinic with a two-month history of frequent loose, bloody stools, often up to three to four times daily, accompanied by significant fecal urgency and occasional mild nocturnal diarrhea. He also reports mild intermittent fatigue but denies fever, significant abdominal pain, or weight loss. On physical examination, vital signs are stable, including a temperature of 36.8°C, heart rate of 72 beats/minute, and blood pressure of 120/78 mmHg. Abdominal examination reveals no tenderness or organomegaly. Digital rectal examination elicits mild discomfort and reveals small streaks of fresh blood on the examining finger. Laboratory evaluation shows no anemia or leukocytosis, and liver function tests are within normal limits. Stool studies, including testing for Clostridioides difficile toxin, are negative. Colonoscopy demonstrates diffuse, continuous inflammatory mucosal changes involving the rectum, characterized by edema, erythema, and friability. An abrupt transition to normal-appearing mucosa is noted just proximal to the rectosigmoid junction, with the remainder of the colon appearing unremarkable. Biopsy specimens obtained from the rectum confirm moderate chronic colitis with crypt architectural distortion and basal plasmacytosis. Considering these findings, what is the most likely diagnosis and the most appropriate initial management approach?

A 38-year-old woman with a history of ulcerative pancolitis, diagnosed 8 years ago, presents for her routine follow-up appointment at an outpatient gastroenterology clinic. She reports well-controlled symptoms with occasional mild, crampy abdominal discomfort and rare, non-bloody diarrhea, occurring fewer than three times per week. Her current medications include daily mesalamine and intermittent rectal glucocorticoid foam for proctitis. She completed a course of oral prednisone six months prior for a mild flare, which resolved completely. Her family history is notable for a paternal aunt with breast cancer but is otherwise negative for inflammatory bowel disease or colorectal cancer. She denies weight loss, fever, or any new systemic symptoms. On physical examination, her vital signs are stable: blood pressure 120/78 mmHg, heart rate 72 bpm, respiratory rate 16 breaths/min, and temperature 37.0°C. Abdominal examination reveals soft, non-tender abdomen with normoactive bowel sounds. There is no hepatosplenomegaly or palpable masses. Given her chronic condition, what is the most appropriate long-term surveillance strategy for colorectal cancer, and what specific histopathological finding on biopsy would most directly necessitate a discussion about prophylactic colectomy?