Two weeks after undergoing allogeneic stem cell transplant for multiple myeloma, a 55-year-old man develops a severely pruritic rash, abdominal cramps, and profuse diarrhea. He appears lethargic. Physical examination shows yellow sclerae. There is a generalized maculopapular rash on his face, trunk, and lower extremities, and desquamation of both soles. His serum alanine aminotransferase is 115 U/L, serum aspartate aminotransferase is 97 U/L, and serum total bilirubin is 2.7 mg/dL. Which of the following is the most likely underlying cause of this patient's condition?

Preformed cytotoxic anti-HLA antibodies

Proliferating transplanted B cells

Newly formed anti-HLA antibodies

A 55-year-old woman recently underwent kidney transplantation for end-stage renal disease. Her early postoperative period was uneventful, and her serum creatinine is lowered from 4.3 mg/dL (preoperative) to 2.5 mg/dL. She is immediately started on immunosuppressive therapy. On postoperative day 7, she presents to the emergency department (ED) because of nausea, fever, abdominal pain at the transplant site, malaise, and pedal edema. The vital signs include: pulse 106/min, blood pressure 167/96 mm Hg, respirations 26/min, and temperature 40.0°C (104.0°F). The surgical site shows no signs of infection. Her urine output is 250 mL over the past 24 hours. Laboratory studies show: Hematocrit 33% White blood cell (WBC) count 6700/mm3 Blood urea 44 mg/dL Serum creatinine 3.3 mg/dL Serum sodium 136 mEq/L Serum potassium 5.6 mEq/L An ultrasound of the abdomen shows collection of fluid around the transplanted kidney with moderate hydronephrosis. Which of the following initial actions is the most appropriate?

Continue with an ultrasound-guided biopsy of the transplanted kidney

Re-operate and remove the failed kidney transplant

Start on pulse steroid treatment or OKT3

Supportive treatment with IV fluids, antibiotics, and antipyretics

A 72-year-old woman presents to the clinic complaining of diarrhea for the past week. She mentions intense fatigue and intermittent, cramping abdominal pain. She has not noticed any blood in her stool. She recalls an episode of pneumonia last month for which she was hospitalized and treated with antibiotics. She has traveled recently to Florida to visit her family and friends. Her past medical history is significant for hypertension, peptic ulcer disease, and hypercholesterolemia for which she takes losartan, esomeprazole, and atorvastatin. She also has osteoporosis, for which she takes calcium and vitamin D and occasional constipation for which she takes an over the counter laxative as needed. Physical examination shows lower abdominal tenderness but is otherwise insignificant. Blood pressure is 110/70 mm Hg, pulse is 80/min, and respiratory rate is 18/min. Stool testing is performed and reveals the presence of anaerobic, gram-positive bacilli. Which of the following increased this patient’s risk of developing this clinical presentation?

Recent antibiotic use for pneumonia treatment

Hypercholesterolemia treated with atorvastatin

Constipation treated with laxatives

Osteoporosis treated with calcium and vitamin D

Peptic ulcer disease treated with esomeprazole

A 59-year-old woman comes to the physician for a routine health maintenance examination. She feels well. She has systemic lupus erythematosus and hypertension. She does not drink alcohol. Her current medications include lisinopril and hydroxychloroquine. She appears malnourished. Her vital signs are within normal limits. Examination shows a soft, nontender abdomen. There is no ascites or hepatosplenomegaly. Serum studies show: Total bilirubin 1.2 mg/dL Alkaline phosphatase 60 U/L Alanine aminotransferase 456 U/L Aspartate aminotransferase 145 U/L Hepatitis A IgM antibody negative Hepatitis A IgG antibody positive Hepatitis B surface antigen positive Hepatitis B surface antibody negative Hepatitis B envelope antigen positive Hepatitis B envelope antibody negative Hepatitis B core antigen IgM antibody negative Hepatitis B core antigen IgG antibody positive Hepatitis C antibody negative Which of the following is the most appropriate treatment for this patient?

Pegylated interferon alpha therapy

Referral to a liver transplantation center

A 66-year-old woman is brought to the emergency department because of fever, chills, night sweats, and progressive shortness of breath for 1 week. She also reports generalized fatigue and nausea. She has type 2 diabetes mellitus and hypothyroidism. Current medications include metformin, sitagliptin, and levothyroxine. She appears ill. Her temperature is 38.7°C (101.7°F), pulse is 104/min, and blood pressure is 160/90 mm Hg. Examination shows pale conjunctivae and small nontender hemorrhagic macules over her palms and soles. Crackles are heard at both lung bases. A grade 2/6 mid-diastolic murmur is heard best at the third left intercostal space and is accentuated by leaning forward. The spleen is palpated 1–2 cm below the left costal margin. Laboratory studies show: Hemoglobin 10.6 g/dL Leukocyte count 18,300/mm3 Erythrocyte sedimentation rate 48 mm/h Urine Protein 1+ Blood 2+ RBCs 20-30/hpf WBCs 0-2/hpf An echocardiography shows multiple vegetations on the aortic valve. Blood cultures grow S. gallolyticus. She is treated with ampicillin and gentamicin for 2 weeks and her symptoms resolve. A repeat echocardiography at 3 weeks shows mild aortic regurgitation with no vegetations. Which of the following is the most appropriate next step in management?

CT scan of the abdomen and pelvis

A 4-month-old boy is brought to the physician by his parents for a well-child examination. He has cystic fibrosis diagnosed by newborn screening. His parents report frequent feedings and large-volume and greasy stools. His 4-year-old brother has autism. Current medications include bronchodilators, pancreatic enzyme supplements, and fat-soluble vitamins. He is at the 18th percentile for height and 15th percentile for weight. Scattered wheezes are heard throughout both lung fields. Examination shows a distended and tympanic abdomen with no tenderness or guarding. Which of the following is a contraindication for administering one or more routine vaccinations?

Fever of 38.2°C (100.7°F) following previous vaccinations

A 43-year-old woman comes to the office with a 5-day history of a rash. She's had a rash across her neck, shoulders, and the palms of her hands for the past five days. She's also had large-volume watery diarrhea for the same period of time. Past medical history is notable for acute myeloid leukemia, for which she received a stem cell transplant from a donor about two months prior. Physical exam reveals a faint red maculopapular rash across her neck, shoulders, and hands, as well as an enlarged liver and spleen. Labs are notable for a total bilirubin of 10. Which of the following is the mechanism of this patient's pathology?

Graft T cells against host antigens

Host CD8+ T cells against graft antigens

Pre-existing host antibodies against graft antigens

Host antibodies that have developed against graft antigens

A 24-year-old woman with 45,X syndrome comes to the physician because of diarrhea for 4 months. She also reports bloating, nausea, and abdominal discomfort that persists after defecation. For the past 6 months, she has felt tired and has been unable to do her normal chores. She went on a backpacking trip across Southeast Asia around 7 months ago. She is 144 cm (4 ft 9 in) tall and weighs 40 kg (88 lb); BMI is 19 kg/m2. Her blood pressure is 110/60 mm Hg in the upper extremities and 80/40 mm Hg in the lower extremities. Examination shows pale conjunctivae and angular stomatitis. Abdominal examination is normal. Laboratory studies show: Hemoglobin 9.1 mg/dL Leukocyte count 5100/mm3 Platelet count 200,000/mm3 Mean corpuscular volume 67 μmm3 Serum Na+ 136 mEq/L K+ 3.7 mEq/L Cl- 105 mEq/L Glucose 89 mg/dL Creatinine 1.4 mg/dL Ferritin 10 ng/mL IgA tissue transglutaminase antibody positive Based on the laboratory studies, a biopsy for confirmation of the diagnosis is suggested, but the patient is unwilling to undergo the procedure. Which of the following is the most appropriate next step in management of this patient's gastrointestinal symptoms?

Intravenous immunoglobulin therapy

Trimethoprim-sulfamethoxazole therapy

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?"

Small bowel transplantation for USMLE Step 1: High-Yield Surgery Lessons

Indications & Contraindications - Gutsy Decisions

Primary Indication: Irreversible Intestinal Failure (IF) with life-threatening complications from Total Parenteral Nutrition (TPN).
Common Causes of IF Leading to Transplant:
- Short Gut Syndrome (<100-150 cm small bowel): Most frequent cause, post-surgical resection (volvulus, necrotizing enterocolitis, trauma).
- Intestinal Motility Disorders: e.g., Chronic Intestinal Pseudo-obstruction (CIPO).
- Congenital Enteropathies: e.g., Microvillus inclusion disease.
Key TPN Complications Forcing Transplant:
- TPN-Associated Liver Disease (PNALD) with progressive fibrosis/cirrhosis.
- Recurrent, severe central line-associated bloodstream infections (CLABSI).
- Thrombosis of ≥2 major central veins.
Absolute Contraindications:
- Active malignancy or untreated infection.
- Severe cardiac or pulmonary disease.
- Active substance abuse or profound non-adherence.

⭐ High-Yield: The development of progressive liver failure (PNALD) is often the critical turning point that pushes a patient with intestinal failure towards transplantation evaluation.

Short Bowel Syndrome: Before and After Surgery

Transplant Types - The Surgical Options

Multivisceral transplant anatomy

Isolated Small Bowel Transplant (ISBTx)
- Indication: Intestinal failure (IF) with preserved liver function.
- The most common type of small bowel transplant.
Combined Liver-Small Bowel Transplant (CLSBx)
- Indication: IF with irreversible intestinal failure-associated liver disease (IFALD).
- The native liver is removed.
Multivisceral Transplant (MVT)
- Indication: Diffuse splanchnic venous thrombosis, locally invasive abdominal tumors (e.g., desmoid), or extensive GI dysmotility.
- Involves stomach, pancreas, duodenum, and small intestine ± liver/colon.

⭐ The transplanted liver in a CLSBx confers an immunological advantage, leading to lower rates of acute rejection of the intestinal graft compared to ISBTx.

Post-Op Management - Rejection & Ruckus

Rejection: Highest rate of all solid organ transplants due to high immunogenicity of gut-associated lymphoid tissue (GALT).
- Acute Cellular Rejection (ACR): Most common, peaks in first 3 months.
  - Signs: ↑ stoma output, fever, abdominal pain, malabsorption.
  - Dx: Endoscopy with biopsy (gold standard) showing crypt apoptosis & villous blunting.

⭐ High stoma output is often the earliest and most reliable clinical sign of acute small bowel rejection.

Histology of acute small bowel transplant rejection

Graft-vs-Host Disease (GVHD): Donor T-cells in the graft attack recipient tissues.
- Classic Triad: Erythematous maculopapular rash, secretory diarrhea, pancytopenia.
- High mortality; may require graft enterectomy.
Infections & Complications:
- CMV: Universal prophylaxis (ganciclovir/valganciclovir) and routine PCR monitoring are critical.
- Post-transplant lymphoproliferative disorder (PTLD): EBV-driven; presents with fever, lymphadenopathy.
ACR Management Flow:

High‑Yield Points - ⚡ Biggest Takeaways

Primary indication is intestinal failure with parenteral nutrition (PN) complications, most notably irreversible liver disease.

Graft types include isolated small bowel, combined liver-small bowel, or multivisceral, tailored to the extent of organ failure.

The gut is highly immunogenic, necessitating potent immunosuppression (e.g., tacrolimus).

Acute cellular rejection is the leading cause of graft loss, diagnosed via endoscopy with biopsy.

High risk for CMV infection and EBV-associated PTLD.

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