Multiple cysts in the kidneys
We have previously talked about autosomal dominant polycystic kidney disease (ADPKD). It is important to distinguish it from acquired cystic kidney disease (ACKD), seen in patients with chronic kidney disease. Following table summarizes the key differences:
| ADPKD | ACKD |
| Family history of ADPKD is present in most patients (new mutation/mosaicism in ~5%) | No family history of ADPKD |
| Kidney function worsens because of enlarging cysts | Typically seen in patients with pre-existing chronic kidney disease/those on dialysis |
| Kidney size is large | Small/normal |
| Typical presentation: Young patient with hypertension or hematuria; or incidental finding while scanning for something else | Seen in patients referred to Nephrology because labs suggested chronic kidney disease (CKD) |
| Extra-renal features are often present (e.g. hepatic/pancreatic cysts, cerebral aneurysm, valvular disease such as mitral valve prolapse) | Absent |
Here are images from a patient with ADPKD and CKD stage 5. Note bilateral super large kidneys that do not fit in one ultrasound frame. If there is a suspicion for cyst-related complications in such patients (infection, malignancy etc.), CT scan or MRI should be obtained instead of relying on POCUS.
In contrast, here are the images from a patient with acquired cystic kidney disease and CKD stage 5. Kidneys are relatively small and echogenic. Diagnosis of ACKD usually involves demonstration of four or more cysts in each kidney and cysts tend to be small (mostly sub-centimeter cysts with occasional larger ones).
Below is another example of ACKD and CKD stage IV. This patient also has calcifications in the medullary pyramids/papillae (note shadowing), possibly related to analgesic use.
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