Bulbar urethral necrosis: current concept and novel comprehensive classification

To elucidate the pathophysiology of bulbar urethral necrosis (BUN), a complex variant of pelvic fracture urethral injury (PFUI) directly related to vascular damage, and propose a novel radiological classification for this entity.

We conducted a descriptive retrospective analysis of 145 patients with BUN treated at our tertiary referral centre from 1995 to 2023. We reviewed their retrograde urethrograms radiological characteristics. Based on the patterns obtained, we developed a BUN radiological classification. Additionally, we reviewed the literature to describe the pathophysiology of BUN.

A total of 145 patients were included in the analysis. The incidence of BUN was 10.8% in the total number of PFUI and 40.3% of complex PFUI. The mean age was 33 years. We observed two repeated radiological patterns: the relation between the penile and bulbar urethra, and the positioning of the distal stump relative to the ischium. BUN was classified into four radiological types. The commonest BUN was Type 3 (35%), followed by Type 2 (26%) and Type 4 (26%), and then Type 1 (13%).

Bulbar urethral necrosis is defined by the absence of a segment of bulbar urethra, typically resulting from previous PFUI repairs. Its pathophysiology is primarily vascular. The most common BUN was Type 3, indicating complete loss of the bulbar urethra. The clinical importance of the proposed radiological classification relies on the prediction of the level of difficulty for substitution urethroplasty.