Can colitis, such as Crohn’s disease or severe ulcerative colitis, cause a psoas abscess?

Can Colitis Cause Psoas Abscess?

Yes, colitis—specifically Crohn's disease—can cause psoas abscess through transmural inflammation and fistula formation, though this is a rare complication occurring in approximately 0.9% of Crohn's disease patients. 1, 2 Ulcerative colitis does not typically cause psoas abscess because its inflammation is limited to the mucosa and submucosa, lacking the transmural penetration necessary for this complication. 3

Mechanism and Pathophysiology

The key distinction lies in the depth of inflammation:

• Crohn's disease exhibits transmural inflammation that extends through all layers of the intestinal wall, enabling penetration and fistula formation that can track to the psoas muscle. 3, 4
• Ulcerative colitis inflammation remains superficial, confined to mucosa and occasionally submucosa only, making psoas abscess formation mechanistically implausible. 3, 4

Psoas abscess in Crohn's disease results from transmural inflammation leading to contained perforation, with subsequent fistulous communication to the retroperitoneal psoas compartment. 5

Clinical Presentation and Diagnostic Pitfalls

Critical caveat: Psoas abscess may be the first manifestation of previously undiagnosed Crohn's disease in up to 24% of cases (11 of 46 reported patients), often without any gastrointestinal symptoms. 1

Classic triad of findings:

• Fever and constitutional symptoms (weight loss, wasting) 6, 7
• Hip flexion contracture and psoas spasm 6, 7
• Wasting of the ipsilateral quadriceps femoris muscle 7

Important pitfall: Patients may lack typical abdominal or gastrointestinal symptoms, presenting only with hip/thigh complaints. 1, 7 Always examine the hip and thigh in patients with known Crohn's disease who develop unexplained fever or weight loss. 7

Diagnostic Workup

When psoas abscess is suspected in the context of colitis:

• CT imaging is the diagnostic modality of choice, demonstrating fluid collection in 11 of 14 patients in one series, or presuppurative changes. 6
• Ultrasonography can identify fluid collections but is less sensitive than CT. 6
• Investigate for underlying Crohn's disease if not previously diagnosed, as this finding mandates exclusion of inflammatory bowel disease. 6

Management Approach

The optimal treatment combines percutaneous drainage, antibiotics, bowel resection of diseased intestine, and antithrombotic prophylaxis. 1

Treatment Algorithm:

1. Initial stabilization: Antibiotics and nutritional optimization (total parenteral nutrition for 12 days if needed) 2

2. Abscess drainage: Percutaneous CT-guided drainage is preferred initially to control sepsis and avoid two-stage surgery 2, 5

3. Definitive surgical management:

   • Resection of fistulous/diseased bowel segment with immediate anastomosis 1, 2
   • Fashion anastomosis remote from abscess cavity 7
   • Long-term drainage (21 days) of abscess cavity to prevent recurrence or fistula formation 7
   • Thromboembolic prophylaxis (complications occurred in 8.3% of patients) 1

Critical evidence on outcomes: Drainage alone resulted in resolution in only 7 of 26 patients (27%), whereas drainage combined with bowel resection achieved cure in 14 of 18 patients (77.8%) after initial procedure. 1 This strongly supports definitive surgical resection rather than drainage alone.

Controversial Area: Immunosuppressive Therapy

The use of anti-TNF-α agents and other immunosuppressives in the setting of active abscess is controversial and potentially hazardous. 5 These should generally be withheld until source control is achieved through drainage and/or resection.

When to Suspect Crohn's Disease as the Cause

Investigate for Crohn's disease when psoas abscess occurs with:

• Young to middle-aged adults (mean age 36 years in primary psoas abscess series) 6
• Right-sided predominance (though can be bilateral) 6
• Absence of other typical causes (vertebral osteomyelitis, urinary tract infection, appendicitis) 6
• Recurrent abscess formation despite adequate drainage 1