What is your diagnosis? The answers

What is your diagnosis?

tHe ANSWeRS…

1. What are the radiographic findings?

there is good serosal detail. the bladder silhouette contains extensive radiolucent/gas opaque streaks and pockets, both within the lumen and conforming to the bladder wall (Figure 2). the prostate gland is moderately enlarged. there is mild ventral vertebral spondylosis deformans noted at L6/L7 and L7/S1.

2. What is the radiographic diagnosis?

the appearance of the urinary bladder is consistent with a diagnosis of emphysematous cystitis. the prostatomegaly in an entire male dog most likely represents benign prostatic hyperplasia, however concurrent prostatic inflammation/infection (i.e. prostatitis) cannot be excluded.

3. What would be the next diagnostic step?

Not all cases of emphysematous cystitis are readily identified from radiographs, particularly if only a small amount of intramural gas is present, or if the bladder is superimposed by intestinal loops. Abdominal ultrasound has therefore been suggested as a more sensitive means for detecting emphysematous changes in the bladder (Petite et al. 2006), and whilst it was not necessary for the diagnosis in this case, the patient was referred for a specialist abdominal ultrasound to look for an underlying cause. the ultrasound revealed a highly abnormal urinary bladder with large amounts of both intraluminal and intramural gas which cast hazy distal acoustic shadows (Figure 3), consistent with severe emphysematous cystitis. Visualisation of the bladder lumen and far wall was hindered by the distal acoustic shadowing artefact, however, the far wall of the bladder had the impression of moderate to severe diffuse thickening. multifocal collections of free peritoneal gas were also identified within the caudal abdomen, likely due to translocation of gas across the bladder wall, however, there was no evidence of free peritoneal fluid. the prostate gland was moderately enlarged with smooth capsular contours and symmetrical lobes, however, there were multiple irregularly shaped and poorly demarcated hypoechoic regions within the parenchyma. the appearance of the prostate was most suspicious for benign prostatic hyperplasia with concurrent prostatitis, although an underlying malignancy could not be entirely excluded without tissue sampling.

Figure 2. The same right lateral abdominal radiograph as in Figure 1. Note the extensive gas streaks and pockets within the bladder lumen and bladder wall (white arrows), and the enlarged prostate gland (red circle).

the liver was also moderately diffusely enlarged with an increase in parenchymal echogenicity and coarsening of echotexture. this hepatopathy/hepatomegaly was the likely cause of the increased ALP found on biochemistry. As a non-specific finding, causes are varied but include vacuolar hepatopathy, hepatitis, cholangiohepatitis, infiltrative neoplasia or nodular regeneration, and tissue sampling would be required for a definitive diagnosis.

Discussion

Emphysematous cystitis (EC) is a form of complicated urinary tract infection, defined by the presence of gas within the bladder wall and lumen (Fumeo

Figure 3. Sagittal ultrasound image of the urinary bladder showing the extensive distal acoustic shadowing artefact due to severe emphysematous cystitis.

et al. 2019). An uncommon disease in veterinary medicine, EC is reported to occur predominantly in animals with diabetes mellitus or primary glycosuria. Fermentation of glucose results in production of carbon dioxide gas, with subsequent gas accumulation within tissues (Petite et al. 2006). In nonglycosuric dogs, EC occurs secondary to other co-morbidities including chronic urinary tract infections, bladder trigone diverticulum, and long-term corticosteroid administration (Petite et al. 2006; Lippi et al. 2019). In these cases, urinary albumin and lactose are thought to act as substrates for gas production (Fumeo et al. 2019). In this patient, urine glucose was negative and the dog was normoglycaemic, thereby excluding diabetes mellitus and primary renal glycosuria as the likely underlying cause of EC. Abdominal ultrasound did not reveal any underlying cause either, although serial ultrasound evaluations may have been more reliable in ruling out structural abnormalities, especially when thorough evaluation was hindered by luminal gas (Lippi et al. 2019). Clinical signs of EC are varied, usually with any combination of lower urinary tract signs including haematuria, stranguria, pollakiuria, urinary incontinence, polyuria and polydipsia (Fumeo et al. 2019). As in this patient, haematuria is reported to be the most common presenting sign (Lippi et al. 2019), and may occur in the absence of other signs. of note, emphysematous pyelonephritis and peritonitis have been reported as rare consequences of EC, stressing the importance of early diagnosis and initiation of appropriate treatment (merkel et al. 2017). Following the radiographic or sonographic diagnosis of EC, aerobic and anaerobic urine cultures and antibiogram should be the next step in the diagnostic workup (Fumeo et al. 2019). In humans with EC, Escherichia coli and Klebsiella pneumoniae are the major pathogens isolated from urine, with approximately 60% of cases associated with E.coli infection (Amano and Shimizu 2014). As in humans, E.coli is the most prevalent isolate from canine EC cases (merkel et al. 2017; Lippi et al. 2019), and whilst culture and susceptibility results were not available for this case, E.coli infection would be the most likely causative organism. treatment for EC should be initiated as soon as a diagnosis is made and consists of appropriate antimicrobial therapy and management of co-morbidities. Susceptibility testing should guide drug selection, and pending results, empirical treatment with a lipid soluble, bactericidal drug with good tissue and urine penetration is appropriate (merkel et al. 2017). Reports on the required duration of treatment are currently lacking. Previous recommendations for the treatment of complicated or recurrent bacterial cystitis in veterinary species was four weeks (Weese et al. 2019), however, no studies focusing specifically on EC currently exist. A review of human EC cases found the median length of treatment to be 10 days (Grupper et al. 2007), suggesting that shorter courses of antimicrobials may be effective in animals as well. Emphysematous cystitis is therefore an uncommon but potential differential for patients with clinical signs attributable to lower urinary tract disease. Given that many of these cases may not undergo diagnostic imaging, the true prevalence of EC is unknown, however the prognosis once identified is good, and most cases of emphysematous cystitis in dogs respond to oral antimicrobials (merkel et al. 2017).

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