In a 6 months old hybrid pig a bilateral alteration was seen of the kidneys. These showed a loss of structure, with an obvious atrophy of the renal medulla and also, to a lesser extent, of the renal cortex parenchyma which presented with a microcystic appearance. The urethers were significantly dilated and thickened.

Histologically the renal parenchyma was almost entirely occupied by cysts lined by a simple epithelium, some of which contained glomerular structures more or less atrophied. In the interstitium fibrosis and a mild mononuclear inflammatory component could be appreciated. Scattered remnants of apparently normal (probably functional) renal parenchyma were also observed .

The lesions observed point to a disturbance of normal renal development causing microcystic structures in virtually all of the renal cortex and a significant loss of renal medulla. Although this can’t be classified into known types of renal lesionin the differential diagnosis we may include:

  • Congenital polycystic kidney. Mutations in the PKD gene(polycystic kidney disease) can result in this type of lesion which is often hereditary.
  • Acquired Polycystic Kidney , perhaps as a result of a chronified interstitial inflammation or due to other causes that can trigger the onset of cysts (hypokalemia, some medications, etc).
  • Renal dysplasia (defect in the formation of nephrons), also congenital. But the focal presence of correctly formed nephrons makes this option less likely.
Pale kidneys, with surface irregularities and atrophy of the medulla and the cortex. Histologically, prominent brown areas correspond to the fraction of normal renal parenchyma.

Pale kidneys, with surface irregularities and atrophy of the medulla and the cortex. Histologically, prominent brown areas correspond to the fraction of normal renal parenchyma.

Up close, a multitude of small cysts can be seen that give a spongy appearance to the parenchyma as well as the lack of renal medulla.

Up close, a multitude of small cysts can be seen that give a spongy appearance to the parenchyma as well as the lack of renal medulla.

Microscopically, all cysts were lined with simple epithelium and among them a few scattered traces of apparently normal renal parenchyma could be observed.

Microscopically, all cysts were lined with simple epithelium and among them a few scattered traces of apparently normal renal parenchyma could be observed.

Some of the cystic cavities contained a renal glomerulus. The interstitium showed fibrosis and in some areas mononucelar inflammatory infiltrate.

Some of the cystic cavities contained a renal glomerulus. The interstitium showed fibrosis and in some areas mononucelar inflammatory infiltrate.