Introduction: Renal replacement lipomatosis is a rare condition that occurs at the end of the spectrum of renal tissue replacement by fat. It is usually unilateral and occurs as a result of severe renal atrophy or destruction usually due to chronic calculus disease, chronic pyelonephritis and renal tuberculosis. The most commonly used diagnostic investigation remains CECT (contrast enhanced computed tomography) scan. Herein we report our series of patients with total renal replacement lipomatosistreated by nephrectomy. Materials & Methods: We retrospectively reviewed our hospital data for cases of RRL, presented and treated during the period Jan. 2006-Dec. 2015. The age, gender, presenting symptoms, clinical and laboratory findings were noted. The indications for surgery, postoperative outcomes and complications were similarly noted and analyzed. Results: Five patients (three females and two males) with a mean age of 48.4 ± 3.2 years presented with symptoms of pain. Computed tomography (CT) in these patients showed the affected kidney to be completely distorted and replaced by ill-defined fatty attenuating lesion. Open nephrectomy was done in all these patients. Histo-pathological report (HPR) revealed features of RRL with renal calculi. Conclusions: Renal replacement lipomatosis is an uncommon entity, and one should have a high index of suspicion when dealing with suspicious lesions similar to xanthogranulomatous pyelonephritis. Specific imaging, operative, and pathological differences may provide clues for the differential diagnosis.
Renal replacement lipomatosis (RRL) is a relatively uncommon disease entity, and is commonly mistaken for xanthogranulomatous pyelonephritis (XGP), which may be due to lack of awareness among urologists, radiologists, and pathologists [
Xanthogranulomatous pyelonephritis is an uncommon renal inflammatory disease characterized by the destruction and replacement of normal parenchyma by sheets of lipid-laden histiocytes, resulting in enlarged renal parenchyma. XGP begins within the pelvis and calyces and subsequently extends into and destroys renal parenchymal and adjacent tissues. All theories agree that the primary factors involved in the development of XGP are bacterial infection, obstruction and calculous disease. Other possible interrelated factors include venous occlusion and hemorrhage, abnormal lipid metabolism, lymphatic blockage, failure of antimicrobial therapy, altered immunologic competence, and renal ischemia [
With the consent obtained from the institutional ethics committee, we retrospectively reviewed the KLES Hospital data for patients undergoing nephrectomy. Inclusion criteria included all cases of RRL that presented to the hospital and treated during the study period Jan. 2006-Dec. 2015. The age, gender, presenting symptoms, clinical and laboratory findings were noted. The indications for surgery, postoperative outcomes and complications were similarly noted and analyzed.
During the study period there were five patients (three females and two males) that fulfilled the criteria of RRL. The mean age at presentation was 48.4 ± 3.2 years. Pain in abdomen, discomfort and vague abdominal mass were the primary presenting symptoms (
No. | Age/Gender | Symptoms | Side | Co-morbidity | Outcome |
---|---|---|---|---|---|
1 | 43/F | Pain, hematuria | R | Renal stone/DM | Nephrectomy |
2 | 52/M | Pain, mass | R | Renal stone | -do- |
3 | 47/F | Pain, mass | L | Renal stone/DM | -do- |
4 | 51/F | Pain, discomfort, mass | L | Renal stone | -do- |
5 | 49/M | Pain, discomfort | R | Renal stone/HTN | -do- |
tomography (CT) in these patients showed the morphology of the affected kidney to be completely distorted and replaced by ill-defined fatty attenuating lesion, with irregular heterogeneous enhancing lesions representing inflammatory changes in the perinephric fat. The radionuclide studies revealed very poorly/non-functioning kidneys. Open Nephrectomy was done in all these patients. The indications for nephrectomy in all these patients were a poorly/non-functioning symptomatic kidney.
Macroscopic examination of the nephrectomy specimen showed an irregular, friable, green/yellow mass replacing the entire renal parenchyma, with a pale and shiny mucosa filled with fine granular calculi. The fatty tissue inside the renal parenchyma was paler than the perirrenal fat, differentiating xanthogranulomatous pyelonephritis from renal replacement lipomatosis. Microscopic examination revealed abundance of chronic inflammatory cell infiltrate with few, isolated, scattered glomeruli and encroachment by adipocytes.
The post-operative period in all the five patients who underwent nephrectomy for RRL was uneventful. The drain and the urethral catheter was removed after 48 hours. All patients took oral feeds within 24 hours following surgery and were discharged from the hospital within 96 hours. Post-operative serum creatinine stabilized to around 1.2 ± 0.325 mg%. The mean follow-up period was 14 months and all patients were doing fine.
During the same study period, six other patients (five females and one male) with a mean age of 54.2 ± 5.7 years underwent nephrectomy for poorly functioning, infected kidneys with histopathological examination revealing xanthogranulomatous pyelonephritis. All these six patients were diabetic with elevated HbA1c (
Renal replacement lipomatosis is an aggressive form of renal sinus lipomatosis. It is usually an unilateral process accompanied by parenchymal atrophy that results from calculousdisease, chronic hydronephrosis, or infection [
Parameters | RRL | XGP |
---|---|---|
Age | 48.4 ± 3.2 | 54.2 ± 5.7 |
Diabetes Mellitus | 40% | 100% |
Urine culture | Negative in all | E. Coli |
Renal stone | 100% | 50% |
HPR | Atrophic renal parenchyma replaced by fatty tissue proliferation | Xanthoma cells infiltrate and substitute necrotic renal tissue resulting in a lipomatous degeneration |
well. RRL usually occurs between the fifth and seventh decade of life. The patient may be asymptomatic or may present with a varied clinical picture, the most common manifestations being urinary tract infections, flank pain, weight loss, hematuria, fever, and palpable mass.
The major differential diagnosis for RRL of the kidney include malakoplakia; fat containing tumors such as angiomyolipomas, lipomas, and liposarcomas; XGP, particularly in the presence of calculi and inflammatory changes ; and transitional cell carcinoma of the renal sinus [
Romero et al. [
Due to the rarity of the disease, one may not have adequate experience to diagnose this entity. Most clinicians would make an initial diagnosis of a solid mass and tumor, and the other probable benign conditions would be ignored. Considering the longtime irritation from a urinary stone and the long disease history, some would even think of the possibility of squamous cell carcinoma (SCC) of the pelvis, although the CT findings would not be compatible with SCC. It is important for urologists to recognize this condition. As the condition is rare and the number in this study is small, one cannot make treatment guidelines or suggest diagnostic tips.
Renal replacement lipomatosis is an uncommon entity, and one should have a high index of suspicion when dealing with suspicious lesions similar to xanthogranulomatous pyelonephritis. Specific imaging, operative, and pathological differences may provide clues for the differential diagnosis.
The authors declare no conflicts of interest regarding the publication of this paper.
Kadeli, V., Nerli, R., Ghagane, S., Hiremath, M.B. and Dixit, N. (2018) Renal Replacement Lipomatosis―A Rare Benign Condition. Surgical Science, 9, 306-310. https://doi.org/10.4236/ss.2018.99037