Cake kidney drained by single ureter: MAG3 renogram for diagnosis and function follow-up

(Section Editor: G. H. Neild)

Raúl Martínez-Lázaro and Anabel Cortés-Blanco

Nuclear Medicine Service, Hospital Universitario Miguel Servet, Zaragoza, Spain

Keywords: cake kidney; diagnosis; function follow-up; single ureter; Tc-99m MAG3 diuretic renogram

Renal history

A 38-year-old man with history of spina bifida, L4–S1 discopathy and azoospermia presented with fever and abdominal pain suggestive of urinary tract infection. An ultrasound showed a ‘cake’ kidney in the pelvis. Intravenous urography, CT and MRI visualized the cake kidney overlying the bladder and drained by single short ureter, with hydronephrosis caused by apparent pelviureteral stenosis (Figs 1Go and 2Go). A Tc-99m MAG3 diuretic renogram showed a single pelvic kidney with delayed excretion of the radiotracer (Fig 3Go and 4AGo). Subsequently, a pyeloplasty was performed. Three months later, renal function was re-assessed by Tc-99m MAG3 diuretic renogram and complete retention of the radiotracer was observed (Fig. 4BGo). Because of the ureteric obstruction a pyelovesicostomy was performed.



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Fig. 1. Intravenous urography showed a single lobulated kidney located in the pelvis.

 


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Fig. 2. MRI imaging detected the cake kidney overlying the bladder and hydronephrosis.

 


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Fig. 3. The cake kidney is visualized by the Tc-MAG3 renogram at the pelvic area.

 


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Fig. 4. (A) Tc-99m MAG3 diuretic renogram showed a single pelvic kidney with a pattern of partially obstructed system showing slight fall in activity after lasix administration (14% of the total injected dose was excreted at 20 min post-injection). (B) Three months later, a Tc-99m MAG3 renogram is that of an obstructed collecting system showing no decrease in activity after lasix administration.

 

Discussion

The synonymous term fused pelvic kidney, cake kidney or lump kidney is defined as an anomaly in which ‘the entire renal substance is fused into one mass, lying in the pelvis, and giving rise to two separate ureters which enter the bladder in normal relationship’ [1]. This is a rare congenital anomaly of the genito–urinary system, and even more so if the kidney is drained by a single ureter, a finding that has been previously reported in only four patients [2]. Renal ectopias may occur simultaneously with other organ malformation [2], and spina bifida was present in our patient.

Cake kidney malformation is not necessarily associated with renal dysfunction or a portend of progressive deterioration of renal function [1], but does require exclusion of concomitant anomalies, long-term follow-up of renal function, and early detection of possible future complications such as obstruction, infection, or calculi. These requirements can be fulfilled by MAG3 diuretic renogram as this technique provides simultaneous kidney visualization and assessment of renal function. Moreover, MAG3 renogram has successfully detected a cake kidney when the nature of the abdominal lump was initially not clear [3]. MAG3 diuretic renogram is a helpful non-invasive cheap tool for diagnosis and long-term follow-up of renal function in cake kidney.

Notes

Correspondence and offprint requests to: Anabel Cortés Blanco, Domingo Ram 32, 3F, Zaragoza, E-50017, Spain. Back

References

  1. Glenn JF. Fused pelvic kidney. J Urol1958; 80: 7–9[ISI][Medline]
  2. Goren E, Eidelman A. Pelvic cake kidney drained by single ureter. Urology1987; 30: 492–493[ISI][Medline]
  3. Srivastava RN, Singh M, Ghai OP, Sethi U. Complete renal fusion (‘cake’/‘lump’ kidney). Br J Urol1971; 43: 391–394[Medline]




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