Answer for BIR CoW 07 Apr 2024
Perinephric abscess with page phenomenon
Findings
Ultrasound showed a well-defined exophytic lesion of mixed echogenicity arising from the upper pole of the left kidney. On ultrasound, it appeared to be an exophytic renal mass. CECT images showed a well-circumscribed peripherally enhancing hypoattenuating lesion in the posterior peri nephric space having close contact with the upper pole of the left kidney but with a negative organ embedded sign suggesting a peri renal rather than a renal origin of the lesion. Associated minimal peri nephric inflammatory changes were also seen. Thin septations were seen at the superior and inferior aspects of this lesion. Ischemic changes were noted in the form of hypo-enhancing areas at the upper pole and mid pole. Similar wedge-shaped hypo enhancement was also seen at mid pole of the right kidney. T2 HASTE axial MRI images of the same patient showed a well-circumscribed hyperintense lesion with a hypointense capsule. There was significant compression over the renal parenchyma. Diffusion-weighted images showed significant restriction with very low ADC values. With the background of diabetes and elevated leukocyte count, a diagnosis of peri renal abscess was given. Hypo-enhancing areas in the left kidney were due to the compressive effect of the abscess compromising the internal perfusion, a sign of page kidney. Hypo-enhancing lesion in the right kidney was reported as focal pyelonephritis.
Discussion
A peri renal abscess is the collection of suppurative material/pus between the renal capsule and para-renal fascia. It is one of the lethal complications of urinary tract infection. Dysuria and increased frequency of micturition are usually not present. These patients usually present with groin pain, insidious onset of fever, or flank pain. They may also present with a palpable mass. In elderly patients and patients with autonomic neuropathy, like in diabetics, or chronic alcoholics, symptoms are indolent. A perinephric abscess develops when an intra-renal cortical abscess ruptures into the perinephric space, especially when it is associated with an obstructing stone. But it can develop directly from acute pyelonephritis causing fat necrosis without the development of intra-renal abscess. This type of presentation makes diagnosis difficult and can be mistaken for exophytic cystic renal cell carcinoma. Peri-renal abscesses are very commonly associated with diabetics and patients with septic emboli. Hematogenous seeding can occur from the liver, cervix, vertebra, gall bladder, and appendix. Perforation of the ureter and calyx is an uncommon cause. Urinalysis may be normal if the abscess does not communicate with the collecting system. It is also normal in patients with hematogenous seeding. So radiological investigation becomes the mainstay for diagnosis. Peri renal collections less than 3 cm are treated with antibiotics. Collections more than 3 cm need image-guided percutaneous drainage. Repeat imaging is needed if there is a persistent abnormality in laboratory parameters, no improvement in the patient`s condition, or if percutaneous drainage is not progressing as expected. Accordingly, in our case, Ultrasound-guided percutaneous drainage was done with pigtail insertion. Microbiological analysis of the pus sample showed the presence of Klebsiella. Follow-up ultrasound showed complete resolution of the collection with relief from renal compression. There was also a significant drop in total leukocyte count.
References:
Okafor CN, Onyeaso EE. Perinephric Abscess. [Updated 2023 Aug 14]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing;2024Jan-.https://www.ncbi.nlm.nih.gov/books/NBK536936/
Findings
Ultrasound showed a well-defined exophytic lesion of mixed echogenicity arising from the upper pole of the left kidney. On ultrasound, it appeared to be an exophytic renal mass. CECT images showed a well-circumscribed peripherally enhancing hypoattenuating lesion in the posterior peri nephric space having close contact with the upper pole of the left kidney but with a negative organ embedded sign suggesting a peri renal rather than a renal origin of the lesion. Associated minimal peri nephric inflammatory changes were also seen. Thin septations were seen at the superior and inferior aspects of this lesion. Ischemic changes were noted in the form of hypo-enhancing areas at the upper pole and mid pole. Similar wedge-shaped hypo enhancement was also seen at mid pole of the right kidney. T2 HASTE axial MRI images of the same patient showed a well-circumscribed hyperintense lesion with a hypointense capsule. There was significant compression over the renal parenchyma. Diffusion-weighted images showed significant restriction with very low ADC values. With the background of diabetes and elevated leukocyte count, a diagnosis of peri renal abscess was given. Hypo-enhancing areas in the left kidney were due to the compressive effect of the abscess compromising the internal perfusion, a sign of page kidney. Hypo-enhancing lesion in the right kidney was reported as focal pyelonephritis.
Discussion
A peri renal abscess is the collection of suppurative material/pus between the renal capsule and para-renal fascia. It is one of the lethal complications of urinary tract infection. Dysuria and increased frequency of micturition are usually not present. These patients usually present with groin pain, insidious onset of fever, or flank pain. They may also present with a palpable mass. In elderly patients and patients with autonomic neuropathy, like in diabetics, or chronic alcoholics, symptoms are indolent. A perinephric abscess develops when an intra-renal cortical abscess ruptures into the perinephric space, especially when it is associated with an obstructing stone. But it can develop directly from acute pyelonephritis causing fat necrosis without the development of intra-renal abscess. This type of presentation makes diagnosis difficult and can be mistaken for exophytic cystic renal cell carcinoma. Peri-renal abscesses are very commonly associated with diabetics and patients with septic emboli. Hematogenous seeding can occur from the liver, cervix, vertebra, gall bladder, and appendix. Perforation of the ureter and calyx is an uncommon cause. Urinalysis may be normal if the abscess does not communicate with the collecting system. It is also normal in patients with hematogenous seeding. So radiological investigation becomes the mainstay for diagnosis. Peri renal collections less than 3 cm are treated with antibiotics. Collections more than 3 cm need image-guided percutaneous drainage. Repeat imaging is needed if there is a persistent abnormality in laboratory parameters, no improvement in the patient`s condition, or if percutaneous drainage is not progressing as expected. Accordingly, in our case, Ultrasound-guided percutaneous drainage was done with pigtail insertion. Microbiological analysis of the pus sample showed the presence of Klebsiella. Follow-up ultrasound showed complete resolution of the collection with relief from renal compression. There was also a significant drop in total leukocyte count.
References:
Okafor CN, Onyeaso EE. Perinephric Abscess. [Updated 2023 Aug 14]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing;2024Jan-.https://www.ncbi.nlm.nih.gov/books/NBK536936/
Note:
We do not discourage differential diagnosis. But all the differentials must satisfy the findings noted in the case.
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The order in which the names appear in this winner's list is based on the time of submission. The first person to send the correct answer gets his/her name on top of the list!
We do not discourage differential diagnosis. But all the differentials must satisfy the findings noted in the case.
If you feel you have answered rightly but cannot find your name in the above list, please call 09551942599.
Did you Know?
The order in which the names appear in this winner's list is based on the time of submission. The first person to send the correct answer gets his/her name on top of the list!