Click on Images for Enlarged View
Findings: On CT, there was a focal area of decreased attenuation and decreased function (contrast excretion) within the right renal parenchyma, with the involved portion appearing swollen. In the involved area, there was also a round, low- attenuation ("cystic") structure with rim enhancement on CECT. On US, there was a round anechoic structure within the right kidney with a mobile debris level. These findings are consistent with Acute/Subacute pyelonephritis and renal abscess formation. The patient was treated with antibiotics. After approximately 7 days with only partial response to therapy, the patient underwent CT-guided percutaneous abscess drainage of the renal abscess.
Diagnosis: Acute/Subacute pyelonephritis and renal abscess formation.
Discussion:
Roles of Imaging:
Imaging is useful in immune-suppressed individuals, or in
cases unresponsive to appropriate ABx therapy, or in
severely ill patients.
1.US: US is a good screening tool, cheaper than CT, and sensitive for identifying dilated renal collecting systems. One can do ICU patients portably. US does, however, have some short-comings: it does not give functional information; it may miss abscesses or perinephric disease.
2.CT: more expensive than US; results in radiation to the patient; carries the risk of contrast reaction. However, CT also gives excellent anatomic detail and functional information (when contrast is administered), it can identify even uncalcified stones, it can evaluate ureters and bladder, and it can evaluate for perinephric disease.
3.MRI: not very specific.
**Can do CT- or US-guided interventions, although CT seems
to be preferred due to better anatomic detail, and
fewer incidences of crossing the pleura with the catheter
(and causing effusion or empyema). Imaging-guided drainage of renal/perirenal
abscesses has been shown to be a safe and effective method
of treatment, with cure rates ranging from 55-94% -
depending on the series - with percutaneous abscess drainage
alone. Common minor complications include: bacteremia (4 in
Lang's series; 4% overall in Lambiase's series), and
unintentional catheter removals. Uncommon major
complications include: hemorrhage and empyema. Problem
Cases include: infected staghorn calculi; infected neoplasms
from GI tract that communicate with GU tract; spinal
osteomyelitis with secondary renal involvement.
References:
1. Textbook of Uroradiology; N. Reed Dunnick; 1991.
2. Upper Urinary Tract Infection: The Current Role of CT,
US, and MRI; by Goldman, Stanford M., et al; Seminars
in US, CT, and MR, vol 12, No 4 (August), 1991: 335-360
3. Percutaneous Drainage of 335 Consecutive Abscesses:
Results of Primary Drainage with 1-Year Follow-up; by
Lambiase, Robert E., et al; Radiology 1992; 184:176-179.
4. Renal and Related Retroperitoneal Abscesses: Percutaneous
Drainage; by Sacks, David, et al; Radiology 1988; 167:447- 451.
5.Renal, Perirenal, and Pararenal Abscesses: Percutaneous
Drainage; by Lang, Erich K.; Radiology 1990; 174:109-113.
6. Percutaneous Abscess Drainage: Editorial Comments;
vanSonnenberg, Eric, et al; Radiology 1992; 184:27-29.
Submitted by: