Ultrasound-Guided Co-Axial Introducer Needle Biopsy in the Diagnosis of Eosinophilic Cystitis in Children
Eosinophilic cystitis (EC) is a rare inflammatory disorder characterized by transmural infiltration of eosinophils within the bladder wall. Clinically, it presents with non-specific symptoms such as urinary frequency, hematuria, dysuria, and suprapubic pain. While EC predominantly affects adults, pediatric cases are exceedingly uncommon, with a median age of diagnosis at 6.5 years. The condition’s etiology remains unclear, though associations with allergic disorders, parasitic infections, and autoimmune conditions have been proposed. Diagnosis is challenging due to overlapping symptoms with more common urinary tract pathologies, and definitive confirmation relies on histopathological evidence of eosinophilic infiltration. Traditional diagnostic methods, such as cystoscopy with mucosal biopsy, are invasive, costly, and often fail to capture submucosal or muscularis involvement, leading to misdiagnosis. This study evaluates the clinical utility of ultrasound (US)-guided co-axial introducer needle biopsy as a minimally invasive, cost-effective alternative for diagnosing EC in children.
Clinical Presentation and Diagnostic Challenges
In pediatric populations, EC often mimics bladder neoplasms or chronic urinary tract infections. The study analyzed 17 children (13 males, 4 females; age range: 3–11 years, mean: 7.3 years) presenting with bladder wall thickening and irritative symptoms. Key complaints included urgency (100%), hematuria (47%), suprapubic pain (29%), and dysuria. Notably, 76% (13/17) of patients had a history of allergies, including food, environmental, or medication sensitivities. Elevated serum immunoglobulin E (IgE) levels (>200 IU/mL) were observed in four patients, further supporting an allergic component. Peripheral eosinophilia (>8%) was present in 82% (14/17) of cases, while urinalysis revealed hematuria in 47% (8/17) and proteinuria in 35% (6/17).
Imaging modalities, including ultrasonography and computed tomography (CT), consistently demonstrated irregular bladder wall thickening, often misinterpreted as neoplastic lesions. However, these findings lacked specificity, necessitating histopathological confirmation. Cystoscopy, the gold standard for bladder evaluation, was performed in two patients prior to referral. It revealed mucosal erythema or bullous lesions, but mucosal biopsies yielded nonspecific chronic inflammation, delaying diagnosis.
Limitations of Cystoscopic Biopsy
Cystoscopy involves visual inspection of the bladder mucosa and targeted biopsy under general anesthesia. While effective for superficial lesions, its utility is limited in EC, where inflammation predominantly affects deeper submucosal and muscular layers. Mucosal biopsies often fail to capture transmural eosinophilic infiltration, resulting in false-negative diagnoses. Additionally, cystoscopy carries risks of urethral trauma, requires general anesthesia in children, and incurs higher costs. These limitations underscore the need for alternative diagnostic approaches capable of obtaining full-thickness bladder wall samples.
Ultrasound-Guided Co-Axial Introducer Needle Biopsy: Technique and Advantages
The study introduces a novel diagnostic technique utilizing US-guided co-axial introducer needle biopsy to obtain full-thickness bladder wall specimens. The procedure is performed under local anesthesia (11 patients) or general anesthesia (6 patients aged ≤5 years). Key steps include:
- Patient Preparation: The patient is placed supine with the abdomen exposed. After disinfection, the puncture site is localized using real-time ultrasound to avoid vascular or neural structures.
- Needle Insertion: A co-axial introducer needle is advanced under US guidance until its outer sheath contacts the outer bladder wall. The inner needle core is then inserted through the sheath into the bladder wall.
- Targeted Biopsy: Under dynamic US monitoring, the needle trajectory is adjusted to ensure passage through the lesion. Three tissue samples (length: ≥10 mm; diameter: 1.4 mm) are extracted from different sites within the thickened bladder wall.
- Specimen Handling: Samples are fixed in formalin for histopathological analysis.
This technique enables sampling of all bladder wall layers, including the submucosa and muscularis, which are frequently spared in cystoscopic biopsies. The coaxial design minimizes tumor seeding risk by shielding the needle track during withdrawal.
Diagnostic Outcomes and Histopathological Findings
All 17 patients achieved definitive diagnoses of EC through US-guided biopsy. Histopathology revealed dense eosinophilic infiltrates within the submucosa and muscularis, accompanied by chronic inflammatory cells and fibrosis in chronic cases. Two patients initially misdiagnosed via cystoscopic biopsy (reported as chronic inflammation) were correctly identified with EC using the US-guided approach. Notably, one patient experienced self-limiting hematuria post-procedure, highlighting the technique’s safety.
Comparative Advantages Over Cystoscopy
- Minimally Invasive: Avoids urethral instrumentation and general anesthesia in most cases.
- Cost-Effectiveness: Reduces hospitalization and anesthesia-related expenses.
- Accuracy: Ensures sampling of all bladder wall layers, critical for detecting submucosal eosinophilic infiltration.
- Safety: Low complication rate (5.9% minor hematuria) compared to cystoscopy-associated risks.
Clinical Implications and Future Directions
The study demonstrates that US-guided co-axial introducer needle biopsy is a reliable, less invasive alternative for diagnosing pediatric EC. Its ability to obtain full-thickness biopsies addresses a critical limitation of cystoscopy, particularly in cases with deep bladder wall involvement. Furthermore, the procedure’s feasibility under local anesthesia reduces psychological and physical trauma in children.
Future research should focus on standardizing the technique, expanding sample sizes, and investigating EC’s predilection for the bladder’s posterior wall (observed in this cohort). Long-term follow-up is also needed to assess the impact of early diagnosis on therapeutic outcomes, as delayed treatment may lead to bladder fibrosis or contracture.
Conclusion
Eosinophilic cystitis remains a diagnostic challenge in pediatric urology due to its nonspecific presentation and limitations of conventional methods. Ultrasound-guided co-axial introducer needle biopsy emerges as a transformative tool, offering high diagnostic accuracy, minimal invasiveness, and cost savings. By enabling targeted sampling of all bladder wall layers, this technique reduces reliance on cystoscopy and mitigates diagnostic delays. Its integration into clinical practice could improve outcomes for children with this rare but potentially debilitating condition.
doi.org/10.1097/CM9.0000000000001564
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