A 46-year-old woman comes to the emergency department because of intermittent abdominal pain and vomiting for 2 days. The abdominal pain is colicky and diffuse. The patient's last bowel movement was 3 days ago. She has had multiple episodes of upper abdominal pain that radiates to her scapulae and vomiting over the past 3 months; her symptoms subsided after taking ibuprofen. She has coronary artery disease, type 2 diabetes mellitus, gastroesophageal reflux disease, and osteoarthritis of both knees. Current medications include aspirin, atorvastatin, rabeprazole, insulin, and ibuprofen. She appears uncomfortable. Her temperature is 39°C (102.2°F), pulse is 111/min, and blood pressure is 108/68 mm Hg. Examination shows dry mucous membranes. The abdomen is distended and tympanitic with diffuse tenderness; bowel sounds are high-pitched. Rectal examination shows a collapsed rectum. Her hemoglobin concentration is 13.8 g/dL, leukocyte count is 14,400/mm3, and platelet count is 312,000/mm3. An x-ray of the abdomen is shown. Which of the following is the most likely cause of this patient's findings?

Colonic diverticular inflammation

A 3-day-old newborn is brought to the physician because of abdominal distention, inconsolable crying, and 3 episodes of bilious vomiting since the previous evening. He was delivered at home at 40 weeks' gestation by a trained midwife. He has not passed meconium. Physical examination shows abdominal distention, a tight anal sphincter, and an explosive passage of air and feces on removal of the examining finger. Abnormal development of which of the following best explains this patient's condition?

Submucosa and muscularis externa

Muscularis mucosae and lamina propria

A 68-year-old man presents to the emergency department with left lower quadrant abdominal pain and fever for 1 day. He states during this time frame he has had weight loss and a decreased appetite. The patient had surgery for a ruptured Achilles tendon 1 month ago and is still recovering but is otherwise generally healthy. His temperature is 102°F (38.9°C), blood pressure is 154/94 mmHg, pulse is 90/min, respirations are 15/min, and oxygen saturation is 98% on room air. Physical exam is remarkable for an uncomfortable and thin man with left lower quadrant abdominal tenderness without rebound findings. Fecal occult test for blood is positive. Laboratory studies are ordered as seen below. Hemoglobin: 10 g/dL Hematocrit: 30% Leukocyte count: 3,500/mm^3 with normal differential Platelet count: 157,000/mm^3 Which of the following is the most appropriate next step in management?

Ciprofloxacin and metronidazole

A 28-year-old male presents to his primary care physician with complaints of intermittent abdominal pain and alternating bouts of constipation and diarrhea. His medical chart is not significant for any past medical problems or prior surgeries. He is not prescribed any current medications. Which of the following questions would be the most useful next question in eliciting further history from this patient?

"Can you tell me more about the symptoms you have been experiencing?"

"Does the diarrhea typically precede the constipation, or vice-versa?"

"Is the diarrhea foul-smelling?"

"Please rate your abdominal pain on a scale of 1-10, with 10 being the worst pain of your life"

"Are the symptoms worse in the morning or at night?"

A 65-year-old man comes to the physician because of abdominal pain and bloody, mucoid diarrhea for 3 days. He has been taking over-the-counter supplements for constipation over the past 6 months. He was diagnosed with type 2 diabetes mellitus 15 years ago. He has smoked one pack of cigarettes daily for 35 years. His current medications include metformin. His temperature is 38.4°C (101.1°F), pulse is 92/min, and blood pressure is 134/82 mm Hg. Examination of the abdomen shows no masses. Palpation of the left lower abdomen elicits tenderness. A CT scan of the abdomen is shown. Which of the following is the most likely underlying cause of the patient's condition?

Focal weakness of the colonic muscularis layer

Twisting of the sigmoid colon around its mesentery

Transmural inflammation of the terminal ileum

Infiltrative growth in the descending colon

Decreased perfusion to mesenteric blood vessel

A 67-year-old man presents to the emergency department with abdominal pain that started 1 hour ago. The patient has a past medical history of diabetes and hypertension as well as a 40 pack-year smoking history. His blood pressure is 107/58 mmHg, pulse is 130/min, respirations are 23/min, and oxygen saturation is 98% on room air. An abdominal ultrasound demonstrates focal dilation of the aorta with peri-aortic fluid. Which of the following is the best next step in management?

Serial annual abdominal ultrasounds

Counsel the patient in smoking cessation

Urgent surgery within the next day

A 24-year-old woman recently noticed a mass in her left breast. The examination shows a 4-cm mass in the left upper quadrant. The mass is firm, mobile, and has well-defined margins. She complains of occasional tenderness. There is no lymphatic involvement. Mammography showed a dense lesion. What is the most likely cause?

Invasive ductal carcinoma (IDC)

Ductal carcinoma in situ (DCIS)

Diverticulitis for USMLE Step 1: High-Yield Surgery Lessons

Pathophysiology - Gut Pouch Punch-Up

False diverticula: Mucosa and submucosa herniate through the muscularis propria.
Occur at weak points in the colonic wall where vasa recta penetrate.
📌 Sigmoid Is The Site: Highest pressure area.

Diverticulosis, hemorrhage, and acute diverticulitis

⭐ The sigmoid colon is the most common site for diverticula (>90% of cases) because it's the narrowest colonic segment, generating the highest pressures via the Law of Laplace.

Presentation & Diagnosis - Bellyache Breakdown

Classic Presentation: Steady, deep LLQ pain, fever, and altered bowel habits (constipation > diarrhea). Nausea and anorexia are common.
- Physical Exam: Localized tenderness, palpable mass (phlegmon/abscess), guarding.
- 📌 Note: Right-sided diverticula (common in Asian populations) can mimic appendicitis.
Diagnostic Workup:
- Labs: Leukocytosis (↑ WBC) is typical.
- Imaging: Abdominal/Pelvic CT with contrast is the gold standard.
  - Key CT Findings: Sigmoid wall thickening (>4 mm), pericolic fat stranding, abscess, fistula.

⭐ High-Yield: Never perform a colonoscopy or barium enema during an acute attack. It dramatically increases perforation risk. A colonoscopy should be done 6-8 weeks post-recovery to exclude underlying malignancy.

Staging & Management - Calming the Chaos

Hinchey Classification (Modified) for Complicated Diverticulitis:
- Stage 1a: Pericolic inflammation/phlegmon
- Stage 1b: Pericolic or mesocolic abscess (<5 cm)
- Stage 2: Pelvic, distant intra-abdominal, or retroperitoneal abscess (≥5 cm)
- Stage 3: Purulent peritonitis
- Stage 4: Feculent peritonitis

CT scan of acute diverticulitis with pericolic abscess

⭐ Elective Sigmoidectomy: Consider after recovery in patients who are young, immunosuppressed, or after a complicated episode to prevent recurrence. The old "two-strikes" rule is no longer absolute; decisions are individualized.

Complications - When Guts Go Rogue

Abscess: Most common complication. Look for persistent fever despite antibiotics. Percutaneous drainage often required if > 4-5 cm.
Fistula: Abnormal connection to adjacent organs.
- Colovesical: Most common; presents with pneumaturia, fecaluria.
- Colovaginal: Passage of flatus/stool from vagina.
Obstruction: Partial or complete blockage from stricture formation due to chronic inflammation.
Perforation: Free perforation leads to purulent or feculent peritonitis (Hinchey stages III/IV).

⭐ High-Yield: The most common fistula type is colovesical, classically presenting with air in the urine (pneumaturia).

High‑Yield Points - ⚡ Biggest Takeaways

Classic triad: LLQ pain, fever, leukocytosis. Sigmoid colon is the most common site.

CT scan with contrast is the best diagnostic test.

Complications include abscess, fistula (colovesical is classic), obstruction, and perforation.

Uncomplicated cases: treat with bowel rest and oral antibiotics.

Complicated cases: require IV antibiotics. Abscesses >4 cm need percutaneous drainage.

Peritonitis or perforation mandates emergency surgery (e.g., Hartmann procedure).

Prevent recurrence with a high-fiber diet after resolution.

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Diverticulitis