A 2-month-old infant boy is brought to the emergency department by his parents presenting with 12 hours of incessant, projectile, bilious emesis. He was born at full term without perinatal complications and has been thriving until this acute onset of symptoms. His parents report he has been increasingly lethargic and irritable, refusing feeds, and had a single episode of dark red, jelly-like stool this morning. On examination, the infant appears listless, with sunken fontanelle and cool, mottled extremities. His abdomen is distended, firm, and diffusely tender to palpation with rebound tenderness. Bowel sounds are diminished. An initial plain abdominal radiograph shows multiple dilated loops of small bowel and absence of gas in the rectum. What is the most likely diagnosis and the immediate critical step in his management?

A 30-year-old woman presents to the emergency department complaining of sudden onset severe, cramping abdominal pain, accompanied by repeated episodes of non-bilious vomiting and abdominal distension for the past 12 hours. She denies any recent travel, significant dietary changes, or prior abdominal surgeries. Her vital signs are: temperature 37.5°C, blood pressure 100/60 mmHg, pulse 118/min, and respirations 22/min. Oxygen saturation is 97% on room air. On physical examination, her abdomen is markedly distended with generalized tenderness, most pronounced in the right lower quadrant, and rebound tenderness. Bowel sounds are diminished, and a tympanitic note is elicited on percussion across the abdomen. An abdominal radiograph (similar to Figure A, depicting the 'coffee bean sign') is obtained. Given this clinical picture, what is the most likely diagnosis and the immediate definitive management strategy?

A 7-day-old infant in the neonatal intensive care unit, admitted for prematurity, suddenly develops bilious emesis and marked abdominal distension. The nursing staff report a decreased frequency of stooling over the last 12 hours, with only scant, dark green meconium noted. Parents recall the infant had been feeding well until this acute change. Prenatal history was uncomplicated, and initial newborn screening was unremarkable. On physical examination, the abdomen is diffusely distended and exquisitely tender to palpation, with absent bowel sounds. Rectal exam reveals an empty vault. Initial abdominal radiographs show multiple dilated loops of small bowel with air-fluid levels. A subsequent upper gastrointestinal contrast study demonstrates a classic "coiled spring" appearance and an abnormal position of the duodenojejunal junction (DJJ) located inferior and to the right of the vertebral column. What is the most likely diagnosis, and what immediate surgical intervention is typically indicated?

A 68-year-old male is admitted to the medical ward from a nursing home with a several-day history of progressive abdominal distension, obstipation, and intermittent colicky abdominal pain. His caregivers report he has not passed stool or flatus for at least 48 hours. On examination, his abdomen is markedly distended and tympanitic, with mild diffuse tenderness but no rebound guarding. Bowel sounds are diminished. Vital signs are stable: BP 125/80 mmHg, HR 92 bpm, RR 16 breaths per minute, and oral temperature 37.2 degrees Celsius. A plain abdominal radiograph demonstrates a markedly dilated loop of colon, characteristic of a 'coffee bean' sign, with the apex pointing towards the right upper quadrant. Considering his presentation and imaging findings, what is the most likely diagnosis, and what immediate therapeutic intervention should be considered to prevent severe complications?

A 48-year-old man with a history of chronic constipation and a prior abdominal surgery for adhesions presents to the outpatient clinic with a 12-hour history of worsening diffuse abdominal pain, distension, and obstipation. He reports intermittent crampy abdominal pain for the past few days, which has now become constant and severe. His primary care physician notes marked abdominal distension and diffuse tenderness and refers him immediately to the emergency department. On arrival, vital signs are T: 37.9 °C, HR: 98 bpm, BP: 130/75 mmHg, RR: 22/min, O2 Sat: 96% on room air. Physical examination reveals a distended abdomen with tympany to percussion, diffuse tenderness to palpation, and absent bowel sounds. There is no rebound tenderness or guarding. A digital rectal exam reveals an empty rectal vault. An abdominal x-ray is shown in Figure A. Given the clinical presentation and initial findings, what is the most likely diagnosis and the appropriate initial non-operative management strategy for this patient?

A 4-week-old girl is brought to the emergency department by her parents due to sudden onset of intractable bilious vomiting that started approximately 6 hours ago. She has become increasingly lethargic, irritable, and has refused all feeds since the vomiting began. Her parents report that she had been developing well, exceeding her birth weight, and had no prior gastrointestinal issues. On arrival, her temperature is 36.0 C, blood pressure is 68/42 mmHg, pulse is 165/min, and respirations are 50/min. Physical examination reveals a pale and listless infant with significantly dry mucous membranes and prolonged capillary refill time of 4 seconds. Her abdomen is markedly distended and tender to palpation, with absent bowel sounds. An abdominal radiograph shows a 'double bubble' sign and paucity of distal intestinal gas. Given these findings, what is the most likely diagnosis and the immediate critical management step?