Polydipsia in a foal with renal helminthiasis.

This research article presents the case of a five-month-old foal showing intense thirst and excessive urination, which was found to be associated with renal helminthiasis – a rare condition characterized by worm infections in the kidneys.

Case Presentation and Initial Findings

• The study describes the case of a foal referred to University College Dublin’s Faculty of Veterinary Medicine with unusually high water consumption. Despite this issue, the foal was alert and in good health, exhibiting no remarkable physical abnormalities.
• When permitted unfettered access to water, the foal drank a much higher volume than the typical range for its species. Furthermore, the concentration of the foal’s urine was lower than normal, indicating excessive dilution due to high water intake.
• Despite these unusual symptoms, routine tests, including counting red, and white blood cells, and measurements of serum chemistry values were within normal ranges.
• Only the foal’s sodium levels were mildly below average, while potassium and calcium levels were normal.

Further Diagnostic Investigation

• Further testing included a water deprivation test and ultrasound examination, leading to the suggestion of idiopathic interstitial nephritis – a type of kidney inflammation in which the cause is unknown.
• To manage the potential washout of key solutes from the kidney due to excessive water consumption, the foal was put on a water restrictive regimen. However, no improvement was reported after a month, and euthanasia was carried out at the owner’s behest.

Final Diagnosis

• After euthanization, kidney examination revealed numerous small white spots spread irregularly across the renal cortex and medulla, raising suspicion about renal helminthiasis.
• Subsequent histopathology of the kidneys, examining the microscopic structure of the tissue, confirmed the presence of helminth infection. However, researchers couldn’t definitively identify the helminth species involved, although the morphology was similar to Halicephalobus deletrix, a specified kidney worm.

Conclusions

• Even though horse kidney worm infections are rare, the authors conclude that they should be considered in diagnosing equine renal diseases, based on the findings of this case.
• Antemortem diagnosis of this condition is challenging as generic diagnostic testing does not provide reliable results. Therefore, in cases suspected of renal helminthiasis, it is advised to conduct a tissue biopsy for more accurate results.
• The paper also discusses the peculiar drinking behavior of the foal, suggesting it suggests psychogenic polydipsia and secondary medullary washout, conditions that could be caused by the renal worm damage and subsequent inflammation.