Indian Journal of Urology
UROLOGICAL IMAGES
Year
: 2017  |  Volume : 33  |  Issue : 2  |  Page : 169--170

The negative pyelogram in urinary obstruction


Onkar Singh, Partho Mukherjee, Antony Devasia 
 Department of Urology, Christian Medical College and Hospital, Vellore, Tamil Nadu, India

Correspondence Address:
Onkar Singh
Department of Urology, Christian Medical College and Hospital, Vellore, Tamil Nadu
India

Abstract

A case of chronic ureteral obstruction secondary to radiation-related ureteral stricture producing a classic “negative pyelogram” on intravenous urography is presented.



How to cite this article:
Singh O, Mukherjee P, Devasia A. The negative pyelogram in urinary obstruction.Indian J Urol 2017;33:169-170


How to cite this URL:
Singh O, Mukherjee P, Devasia A. The negative pyelogram in urinary obstruction. Indian J Urol [serial online] 2017 [cited 2019 Dec 10 ];33:169-170
Available from: http://www.indianjurol.com/text.asp?2017/33/2/169/203424


Full Text



 Introduction



The radiological signs of acute and chronic obstruction of urinary tract are well described. “Rim sign” and “crescent sign” are the commonly described signs in relation to chronic obstruction. However, “negative pyelogram” is another sign of longstanding obstruction that has been rarely illustrated.

 Case Report



A 54-year-old woman presented with left flank pain and lower urinary tract symptoms. She had received radiation therapy 20 years earlier for cervical carcinoma. Examination and urinalysis were normal. Ultrasonography revealed left hydroureteronephrosis. Intravenous urography (IVU) showed prompt excretion of contrast from the right kidney with a well-opacified pelvicalyceal system (PCS) and ureter sequentially. However, the left side showed a dense left nephrogram, followed by a characteristic negative pyelogram [Figure 1]. A grossly dilated renal pelvis with ballooning of calyces was seen on the negative pyelogram image that correlated with the ultrasonographic images of the left kidney [Figure 2].{Figure 1}{Figure 2}

 Discussion



IVU and computerized tomography are extensively used for the evaluation of ureteral obstruction. The parenchymal “rim sign” has been classically described for longstanding high-grade ureteral obstruction that can be seen on any contrast-enhanced imaging study.[1] In chronic obstruction, a high hydrostatic pressure in the PCS leads to compression and atrophy of the renal parenchyma. A thin, atrophic renal parenchyma may still have some concentrating ability. Enhancement of this residual parenchyma surrounding the dilated PCS is seen as “rim sign” on contrast imaging. However, further excretion of contrast into the PCS may not occur initially due to the high hydrostatic pressure in the PCS. Unopacified urine in the dilated PCS surrounded by opacified parenchyma is seen as a lucent “negative pyelogram” [Figure 1]. At the same time, the contralateral kidney and PCS if unobstructed will show exactly the opposite image, i.e., normal (or positive) pyelogram because of the opacified PCS and unopacified parenchyma. “Negative pyelogram” is seen in the early phases of contrast studies. Depending on the degree of function of the residual renal parenchyma,[1],[2] the excretion of contrast into the obstructed PCS may be seen on delayed imaging, diluting the “negative pyelogram.” This is probably the reason why a “negative pyelogram” is not as commonly seen and illustrated as the “rim sign.” Although both of these signs are similar in terms of the underlying disease process, “rim sign” is typically labeled when the renal parenchyma is seen as a very “thin rim of tissue.” “Negative pyelogram” indicates the presence of residual functional renal parenchyma.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

References

1Dyer RB, Chen MY, Zagoria RJ. Classic signs in uroradiology. Radiographics 2004;24 Suppl 1:S247-80.
2Burgener FA, Kormano M. Differential Diagnosis in Conventional Radiology. 2nd Revised Edition. New York: Thieme Medical Publishers, Inc.; 1991. p. 131.