September 7, 2022

Hydronephrosis is a condition where excess urine accumulates in the kidney(s) and causes swelling within the organ. This condition causes pain during urination, nausea and vomiting.

The unobstructed flow of urine from the kidneys to the bladder, and from the bladder through the urethra, is essential to preserve renal function.  Hydronephrosis can occur at any level of the ureter.

Causes of upper tract obstruction include renal or ureteral stones, congenital abnormalities, ureteral strictures or extrinsic compression of the ureter secondary to malignancy or inflammatory conditions.

When a patient has hydronephrosis and an infection, whether a kidney infection or an unspecified UTI, this is coded to N13.6, Pyonephrosis. This code includes both hydronephrosis and infection.

The presence of a stone is included in code N13.6, as well and not separately reported.

According to the code book, hydronephrosis with infection takes us to N13.6 by looking up “hydronephrosis, with, infection”.

Also, according to the code book, calculus with infection takes us to N13.6 by looking up calculus, urinary, with hydronephrosis, with infection.

It also states under the Tabular in ICD-10-CM, N13.6:

  • N13.6 Pyonephrosis
    • Conditions in N13.0 – N13.5 with infection
    • Obstructive uropathy with injection
    • Use Additional Code (B95-B97, to identify infectious agents.



Alicia R. Blamble| RHIA

Managing Auditor | Excite Health Partners


Reference:  ICD-10-CM, American Urological Association.