# Radiographic Appearance of the Urinary Bladder and Application of a Vertebral Bladder Score for Evaluating Bladder Size in Healthy Guinea Pigs (Cavia porcellus) and Guinea Pigs with Clinical Signs of Cystitis

## TL;DR

This study describes how the urinary bladder appears on X-rays in guinea pigs with bladder inflammation and introduces a new scoring system to assess bladder size.

## Contribution

The study introduces a vertebral bladder score (VBS) for objectively evaluating bladder size in guinea pigs with cystitis.

## Key findings

- Guinea pigs with cystitis had larger bladders and increased bladder opacity compared to healthy ones.
- A vertebral bladder score (VBS) above 1.3 LVU correlated with the presence of cystitis.
- Radiographic signs like bladder stones and cloudy material were more common in guinea pigs with cystitis.

## Abstract

Urinary bladder inflammation, also known as cystitis, is a common and painful condition in pet guinea pigs that can markedly reduce their quality of life. Diagnosis is often challenging, and little information is available on the normal radiographic appearance of the guinea pig urinary bladder. In this study, we aimed to describe the size and appearance of the urinary bladder on radiographs in healthy guinea pigs and to compare these with those in guinea pigs showing clinical signs of cystitis. Radiographic images from 24 healthy animals were compared with those from 24 guinea pigs affected by cystitis. Guinea pigs with cystitis more frequently showed cloudy or mineral-like material within the urinary bladder and bladder stones. Their urinary bladders were also larger than those of healthy guinea pigs. To support an objective evaluation of urinary bladder size, we applied a simple measurement method based on the bones of the spine. The results show that radiographs can provide valuable information for identifying urinary bladder disease in guinea pigs and may help veterinarians diagnose cystitis more reliably, thereby improving animal welfare, but future larger studies are needed to confirm these results.

The radiographic appearance of the urinary bladder in guinea pigs (Cavia porcellus) affected by cystitis is poorly characterized. This retrospective case–control study assessed the radiographic characteristics of the urinary bladder (digital abdominal and whole-body radiographs) in 24 healthy guinea pigs and 24 guinea pigs diagnosed with cystitis. Inclusion criteria for the cystitis cohort included presence of clinical signs (hematuria, incontinence, stranguria, abdominal discomfort, apathy, and inappetence), leukocyturia and/or bacteriuria, complemented by right lateral radiographs and either ultrasound or a positive urine culture. Radiographic criteria indicative of cystitis were systematically evaluated using a vertebral bladder score (VBS) expressed in lumbar vertebral units (LVU) and reference marker lines on lateral radiographs to assess urinary bladder distension. Compared to the control group, radiographs of guinea pigs with cystitis demonstrated increased bladder opacity (46% of cases) and solitary uroliths (25%). Bladder height in patients with cystitis exceeded that of healthy counterparts (median: 16.6 vs. 13.0 mm). The VBS in the cystitis group was significantly elevated (median: 1.50 vs. 1.20 LVU). This investigation revealed that enhanced bladder distension and increased bladder opacity, with a VBS surpassing 1.3 LVU, correlated with the presence of cystitis.