Lizard Urinary System

The kidneys are metanephric in all species. In iguanas they lie within the pelvic canal on either side of the colon. Nephromegaly can result in obstruction of the colon as it passes between the kidneys within the pelvic canal.

• Granulomatous nephritis causing colonic obstruction or dystocia is relatively common in the green iguana.
• The posterior segment of the kidney (called sexual segment) in some male geckos, skinks and iguanids is sexually dimorphic. It swells during the breeding season, contributing to the seminal fluid; its colour may also change dramatically and should not be misinterpreted as pathology.

Uric acid is the main form of nitrogenous waste with lesser amounts of ammonia and urea depending on the species, the natural environment and degree of water conservation required. Uric acid is excreted by tubular secretion rather than urea by glomerular filtration.

Most lizards have a urinary bladder where the urine may be modified. Urinalysis may therefore not indicate renal function. The bladder is present in most lizards and helps water retention. It connects to the cloaca by a short urethra. Reflux urine is concentrated.

References

• Mader, D.R. (2005). Reptile Medicine and Surgery. Saunders. pp. 1264. ISBN 072169327X