Metabolic Derangement in Ileal Conduits
Which metabolic derangement is most commonly associated with an ileal conduit urinary diversion?
The most common metabolic derangement associated with an ileal conduit is metabolic acidosis. This occurs because the ileum segment used in the conduit is responsible for absorbing chloride ions and secreting bicarbonate ions. As a result, patients with an ileal conduit have an increased loss of bicarbonate in their urine, leading to a decreased blood bicarbonate level and subsequent metabolic acidosis. In addition, the increased absorption of chloride ions can contribute to hyperchloremic acidosis. Hyperchloremic metabolic acidosis is rare if the conduit works well and drains appropriately - especially in ileal conduits (compared to when the transverse colon segment is used, the ileum does not absorb that much chloride). However, if the urine is not draining appropriately, stagnation causes increased absorption. Therefore, a loopgram should be considered in this scenario. Hypokalemia can be associated with ileal conduit urinary diversion, but it is not as common or directly related to the ileal conduit as metabolic acidosis. Hypokalemia may be a secondary consequence of the body's response to metabolic acidosis. In order to maintain acid-base balance, the kidneys will excrete more hydrogen ions (protons) in response to metabolic acidosis. To do so, the kidneys may increase the secretion of potassium ions and hydrogen ions, decreasing blood potassium levels and hypokalemia. Therefore, while hypokalemia can be associated with ileal conduit urinary diversion, it is less directly related and common than metabolic acidosis.
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