In an HIV‑positive neutropenic patient with bandemia, elevated procalcitonin and elevated lactate who shows circumferential thickening of the ascending colon and hepatic flexure on imaging, what are the most likely diagnoses and how should they be managed emergently?

Neutropenic Enterocolitis (Typhlitis) in HIV-Positive Neutropenic Patient

In this HIV-positive neutropenic patient with circumferential ascending colon thickening, bandemia, elevated procalcitonin, and initial elevated lactate, neutropenic enterocolitis (typhlitis) is the most likely diagnosis and requires immediate broad-spectrum antibiotics, bowel rest, and early surgical consultation—while CMV colitis remains an important differential that may require antiviral therapy if the patient fails to improve within 48-72 hours. 1, 2

Most Likely Diagnosis: Neutropenic Enterocolitis

Neutropenic enterocolitis is the commonest cause of acute abdominal pain in neutropenic patients and has a mortality rate reaching 29.5% if misdiagnosed or underestimated. 1 The clinical presentation—neutropenia with bandemia, fever (implied by elevated procalcitonin), circumferential colonic wall thickening from ascending colon to hepatic flexure, and elevated lactate—creates a classic picture of typhlitis. 1, 2

Key Diagnostic Features Supporting Typhlitis

• Bowel wall thickening >10 mm on CT carries a 60% mortality risk versus only 4.2% when <10 mm, making urgent contrast-enhanced CT the gold standard for both diagnosis and prognostication. 1, 2, 3
• The ascending colon and hepatic flexure involvement is consistent with typhlitis, which classically affects the cecum, terminal ileum, and right colon. 2
• Neutropenic enterocolitis can occur in HIV patients even without chemotherapy exposure, though it typically develops 1-2 weeks post-chemotherapy in cancer patients. 4, 5
• Elevated lactate suggests bowel ischemia or impending perforation, which are absolute surgical indications. 2, 3

Immediate Emergency Management Algorithm

Step 1: Initiate Broad-Spectrum Antibiotics Immediately

Start piperacillin-tazobactam OR a carbapenem (imipenem-cilastatin or meropenem) as monotherapy to provide anti-pseudomonal and anaerobic coverage. 2, 3 This follows IDSA guidelines for febrile neutropenia and covers the enteric gram-negatives, gram-positives, and anaerobes that invade the damaged bowel wall. 1, 2

• If MRSA or resistant enterococci are suspected based on local epidemiology or prior cultures, add vancomycin. 3
• If no clinical improvement occurs within 48-72 hours, add empirical antifungal therapy (amphotericin B or fluconazole) because fungemia is common in non-responders. 2, 3, 6

Step 2: Enforce Strict Bowel Rest and Supportive Care

• Strict NPO status with nasogastric decompression to limit bowel distension and reduce perforation risk. 2, 3
• Aggressive IV fluid resuscitation to correct the elevated lactate and maintain perfusion. 2, 3
• Total parenteral nutrition if prolonged ileus is anticipated. 2
• Administer G-CSF (granulocyte-colony stimulating factor) to accelerate neutrophil recovery; symptom resolution correlates directly with rising neutrophil counts. 2, 3

Step 3: Obtain Early Surgical Consultation

Early surgical consultation is mandatory even while pursuing medical management, given the high mortality (57-81%) when emergency surgery becomes necessary. 2, 6 Surgery should be reserved for specific complications, but the surgeon must be involved from the outset. 1

Absolute surgical indications include: 2, 3

• Free intraperitoneal air (perforation) on imaging
• Absent bowel-wall enhancement indicating ischemia
• Persistent GI bleeding despite correction of thrombocytopenia and coagulopathy
• Clinical deterioration despite maximal medical therapy (worsening sepsis, rising lactate, hemodynamic instability)
• Abscess formation requiring drainage

Step 4: Serial Monitoring

• Serial abdominal examinations every 4-6 hours to detect early perforation or deterioration. 3
• Repeat CT imaging at 48-72 hours if no clinical improvement or if the patient worsens. 3
• Monitor complete blood count, lactate, and procalcitonin trends. 3

CMV Colitis as Important Differential

CMV colitis must be considered in this HIV-positive patient, particularly if CD4 count is <50 cells/μL or if the patient fails to improve on antibacterial therapy. 1 However, the acute presentation with bandemia and elevated lactate favors bacterial typhlitis over CMV.

When to Suspect CMV

• If fever persists beyond 48-72 hours despite appropriate antibiotics, consider adding ganciclovir or foscarnet for presumptive CMV. 2, 3
• CMV colitis typically presents more indolently than typhlitis, though it can cause similar imaging findings. 1
• Flexible sigmoidoscopy with biopsies can confirm CMV (showing characteristic "owl's eye" inclusions), but colonoscopy is contraindicated in typhlitis due to very high perforation risk. 2

Additional Diagnostic Workup

• Test for Clostridioides difficile toxin in all cases of diarrhea with or without acute abdomen. 1
• Blood cultures and stool cultures to identify specific pathogens and guide antimicrobial therapy. 3, 6
• Consider HIV-specific pathogens including Mycobacterium avium complex and abdominal tuberculosis, especially if CD4 count is low. 1

Critical Medications to Avoid

Anticholinergic, antidiarrheal, NSAID, and opioid agents are contraindicated because they mask clinical deterioration, aggravate ileus, and can precipitate toxic megacolon. 2, 3, 6

Expected Outcomes and Prognosis

• Approximately 70-86% of patients achieve resolution with conservative management within 6-8 days once neutropenia is corrected. 1, 2, 3
• Mortality ranges from 5% with optimal medical management to 81% when emergency surgery is required during active neutropenia. 2
• Premature surgery in stable neutropenic patients without documented perforation or ischemia results in worse outcomes than continued medical management. 3

Common Pitfalls to Avoid

• Delaying CT imaging based on equivocal physical exam findings—clinical signs are unreliable in immunocompromised patients. 6
• Failing to obtain early surgical consultation—even if pursuing medical management, the surgeon must be involved from the start given high mortality. 6
• Using antidiarrheal agents—these worsen ileus and mask deterioration. 6
• Delaying repeat imaging when the patient fails to improve—bowel wall thickness >10 mm predicts 60% mortality. 2, 3
• Operating prematurely without clear indications—exhaustive medical management should be pursued first unless perforation or ischemia is documented. 3