abnormal renal tubule morphology abnormal proximal convoluted tubule morphology abnormal proximal renal tubule MPheno.ontology MP:0004756 abnormal proximal kidney tubule abnormal proximal tubule any structural anomaly of the convoluted portion of the duct system of the nephron that extends from the renal glomerular capsule in the kidney cortex into the kidney medulla where it joins the loop of Henle; fluid entering the proximal convoluted tubule is reabsorbed into the peritubular capillaries, including approximately two-thirds of the filtered salt and water and all filtered organic solutes; the most distinctive characteristic of the proximal tubule is its brush border (or striated border), not found in the distal convoluted tubule