Renal tubular acidosis in two horses: diagnostic studies.

The research article discusses the diagnosis and investigation of renal tubular acidosis (RTA), a kidney disease, in two horses. The researchers performed a series of tests to identify the type and cause of RTA but were unable to determine the causative factors despite confirming the diagnosis.

Examination and Diagnosis

• Two horses, an 11-year-old Quarter Horse mare and a 2-year-old Quarter Horse colt were given to the University of California Veterinary Medical Teaching Hospital after they were clinically diagnosed with Renal Tubular Acidosis (RTA). RTA is a medical condition that involves the failure of the kidneys to properly acidify urine.
• The researchers conducted endogenous creatinine clearance and sodium sulfanilate clearance tests on the horses. These tests evaluate glomerular function, an integral part of the urine formation process in the kidneys. The test results were found to be within the reference ranges, and no abnormality in glomerular function was observed.

Acid Loading Test

• An acid loading test was performed to assess how the renal tubular function of the horses would respond. This involved each horse being orally administered with a solution consisting of ammonium chloride (NH4Cl) and water.
• The researchers found that the urine acidification in response to the orally administered acid load was less than that observed in control horses. This suggested that the horses were not effectively excreting acid in their urine, a characteristic symptom of RTA.
• The urinary clearance ratio for sodium was also found to be greater in these horses compared to the controls. This observation further supported the diagnosis of RTA.
• The findings indicated a diagnosis of RTA that closely resembled type 1 or distal RTA. Distal RTA is a type of RTA where the primary defect is in the kidney’s ability to remove acid or lower urine pH.

Investigation of RTA Causes

• Despite confirming the diagnosis of RTA, the cause of the disease remained unknown.
• The researchers attempted to determine the cause of the RTA in these horses by carrying out renal ultrasonography, renal biopsy, and a mating study. These tests were designed to identify physical abnormalities or genetic factors respectively that might be causing RTA. However, no such abnormalities or factors were identified.

Conclusion

• In conclusion, while the study was able to confirm RTA in the two horses, it did not succeed in figuring out the cause. This highlights the often complex and insidious nature of this kidney disease and underscores the need for continued research and advanced diagnostic methods.