What is the best course of action for an elderly female patient with left-sided flank and back pain, status post (after) appendectomy (surgical removal of the appendix) about a month ago, with normal urinalysis (urine test) results and no fever?

Evaluation and Management of Post-Appendectomy Left Flank Pain in an Elderly Patient

Immediate Clinical Assessment

This patient requires urgent CT imaging with IV contrast to evaluate for post-operative complications, despite the normal urinalysis and absence of fever. 1

The presentation of left-sided flank and back pain one month after appendectomy in an elderly patient, even with normal urine and no fever, raises serious concern for delayed post-operative complications that can present atypically in this age group.

Key Diagnostic Considerations

Why This Presentation is Concerning

• Post-appendectomy abscesses can present with atypical pain patterns, including contralateral (left-sided) flank pain, and may occur weeks to months after surgery, as documented in cases where hepatic abscesses presented as back pain 8 months post-operatively 2

• Elderly patients with intra-abdominal pathology frequently present without typical inflammatory markers - they may lack fever and have delayed or absent laboratory abnormalities due to age-related changes in immune response 3

• The absence of fever does not exclude serious post-operative complications in elderly patients, who often demonstrate blunted inflammatory responses 3

Differential Diagnosis Priority

The most critical diagnoses to exclude include:

• Residual or recurrent intra-abdominal abscess - can present with referred pain patterns and may not cause urinary abnormalities 2

• Retained appendicolith or incomplete source control - elderly patients have higher rates of complicated appendicitis (18-70%) and structural weakness predisposing to perforation 3, 4

• Colonic pathology - elderly patients with appendicitis require elective colonic screening, as malignancy can present with similar symptoms 3, 4

• Musculoskeletal causes - though less urgent, neurogenic or referred pain patterns can occur 5

Recommended Diagnostic Approach

Immediate Imaging

• Order CT abdomen/pelvis with IV contrast immediately - CT has 100% sensitivity and 99.1% specificity for intra-abdominal pathology and is rated "usually appropriate" (8/9) by the American College of Radiology for post-operative complications 1

• Do not delay imaging based on normal laboratory values - in elderly patients, unelevated WBC and CRP together had 100% negative predictive value for appendicitis in one series, but this does not apply to post-operative complications where the clinical context is entirely different 6

Laboratory Evaluation

While awaiting imaging, obtain:

• Complete blood count with differential - neutrophil percentage >75% is the most sensitive marker (82% sensitivity) for intra-abdominal infection 1

• C-reactive protein - values >101.9 mg/L suggest complicated disease in elderly patients 1

• Procalcitonin - has an AUC of 0.94 for identifying complicated intra-abdominal infections 1

Critical Clinical Pitfalls to Avoid

• Do not assume left-sided pain excludes right-sided pathology - post-operative abscesses can cause referred pain patterns and may migrate or present contralaterally 2

• Do not be falsely reassured by normal urinalysis - this only excludes primary urinary tract pathology, not intra-abdominal complications 1

• Do not wait for fever to develop - elderly patients have significantly higher mortality (8% vs <0.1% in younger patients) and often present without classic inflammatory signs 7

• Remember that elderly patients have 25% complication rates with negative appendectomy versus 3% in younger patients, making any post-operative symptoms particularly concerning 1

If Imaging Reveals Complications

• Appendicular abscess: Percutaneous drainage if accessible, with broad-spectrum antibiotics for 3-5 days based on clinical response 3

• Diffuse peritonitis or free perforation: Urgent surgical consultation for operative management 3

• No acute findings: Consider colonic screening given the strong recommendation for all elderly post-appendectomy patients, and evaluate for alternative causes including malignancy 3, 4

Antibiotic Considerations if Infection Confirmed

• Initiate broad-spectrum coverage (e.g., piperacillin-tazobactam or cephalosporin/fluoroquinolone plus metronidazole) if abscess or complicated infection identified 8

• Duration should be 3-5 days, with discontinuation based on clinical criteria (resolution of fever, normalized leukocytosis) rather than arbitrary time frames 3