Abstract
Multicystic dysplastic changes in one half of a horseshoe kidney is an uncommon presentation. Surgical resection of the affected kidney is the treatment of choice. Accurate pre-operative evaluation ensures adequate planning, treatment and optimal outcome.
We report the successful management of a 2-year old male child with massive abdominal distension due to multicystic dysplasia of the left half of a horseshoe kidney. Existing literature is reviewed and the challenges of management in this environment are highlighted.
Keywords: Horseshoe kidney, Multicystic Dyspalsia, Unusual presentation
Introduction
The horseshoe kidney is an anatomical fusion anomaly where the upper or lower poles of the kidneys are joined at a midline or paramedian isthmus by fibrous or renal parenchymal tissue. It is a renal fusion anomaly occurring in 1:400-800 live births with a 2:1 male : female ratio1. A fibrous isthmus is thought to be due to mechanical fusion during development, while abnormal migration of posterior nephrogenic cells explains the renal parenchymatous isthmus. Usually, there is higher incidence of associated pathologies in horseshoe kidney which include vesicoureteric reflux , pelviureteric junction obstruction, urinary system calculi, urinary tract infections and urinary system malignancies. Others such as genitourinary, skeletal and cardiovascular anomalies are also common.
Multicystic dysplastic kidney is the commonest cystic disease of the kidney with incidence of 1 in 2400 live births. Since Spence identified multicystic dysplastic kidney as an entity in 19552, it has been well defined as a congenital anomaly where the renal cortex is replaced by cysts of varying sizes in a background of dysplastic renal parenchyma. It is essentially a unilateral disease in live patients as bilateral cases are incompatible with life. Multicystic dysplastic kidney may be the classic hydronephrotic, or solid cystic variant. Emrbryologically, it is thought to be due to early ureteric obstruction or abnormal induction of metanephric blastema by ureteric bud. Spontaneous involution over time is common but in a few cases the cysts progressively enlarge becoming symptomatic and requiring excision.
Unilateral occurrence of multicystic dysplastic kidney in a horseshoe kidney is an uncommon congenital anomaly3,4. It may be detected on prenatal ultrasound3, during childhood4 or in adult life. Symptomatic cases may present with recurrent abdominal pain, fever or abdominal mass.
This paper seeks to report this uncommon condition and to highlight some challenges in the management.
Case Report
A 2-year-old male child presented with a cystic abdominal mass of five months duration. The onset was gradual but progressive beginning from the left flank and crossing the midline to involve the entire abdomen. There was no associated cough, weight loss, hematuria, fever or changes in bowel and urinary habits. He remained active despite his massively enlarging abdomen. There were no remarkable previous medical or obstetrics histories.
The child weighed 19kg with an abdominal girth of 81cm and a reduced air entry at the lung bases. His blood pressure, hemoglobin level as well as serum biochemistry were within normal limits.
Abdominal ultrasound showed huge multi-septate cystic intra-abdominal mass continuous from the right kidney and displacing the abdominal organs. The left kidney was not visualized and a horseshoe kidney was not suspected. Intravenous urography showed complete absence of function of the left kidney and delayed excretion in the right kidney with marked lateral displacement of the ipsilateral ureter and dilated renal pelvis. The patient was unable to afford computed tomography and magnetic resonance imaging scans and was not on health insurance.
Exploratory laparotomy revealed massive cystic dilation of the left moiety of a horseshoe kidney containing amber fluid, with an attached atretic left ureter. This was not suspected preoperatively using the abdominopelvic ultrasonography and intravenous urography.The right renal moiety was normal with tortuous, laterally displaced ureter and a dilated extrarenal pelvis. A right paramedian avascular cleavage plane existed between the two parts of the horseshoe kidney, allowing easy demarcation and excision of the diseased left cystic component. The excised mass weighed 7.1kg (58.3% of child’s pre-operative weight). The other abdominal organs were normal.
The patient made an uneventful post-operative recovery. He was discharged home on the 9th post operative day and has remained symptom free after a follow-up period of 3 years. The histology report confirmed the diagnosis of multicystic renal dysplasia with no evidence of malignancy.
Conclusions
Discussion
Multicystic dysplastic kidney is usually unilateral as bilateral cases are not compatible with life. The presence of multicystic dysplastic kidney disease in a horseshoe kidney indicates that the fusion of the kidneys was a later event. The aetiological theory of fusion in a horseshoe kidney is also confirmed in our patient as a fibrous avascular plane between the fused left and right kidneys made excision easy.
The low prevalence of this anomaly makes large scale studies difficult. Literature search revealed mainly case reports and small case series as in Borer JG et al5 where 3 cases of unilateral multicystic dysplasia in horseshoe kidney was reported. In utero diagnosis has been reported3, but prenatal ultrasonography in our index patient showed no anomaly. This may be because of the small fetal size or an observer error.
It is more common for multicystic dysplastic kidney to gradually involute or remain static in size, but in our patient, it gradually enlarged. Horseshoe kidney only became obvious intraoperatively as preoperative ultrsonography and intravenous urography were not suggestive. Computed tomography scan and magnetic resonance imaging could have diagnosed horseshoe kidney pre-operatively and aided planning of surgical treatment as recommended by Borer JG et al in their series5 .
The systolic and diastolic blood pressures remained normal in this patient contrary to a report by Snodgrass WT6.In his case series Snodgrass associated multicystic dysplastic kidney with elevated systolic blood pressure in 50% of cases.
Despite the large size of cyst, there was no weight loss. There was also no evidence of gastric outlet obstruction nor malignancy as opposed to some other case reports in which multicystic dysplastic kidney caused gastric outlet obstruction7 and harbored various malignancies8,9 . Also, there was no respiratory distress which when present may require percutaneous decompression of the distended abdomen10. The fluid in the cyst was amber on gross examination, though the histology report showed pyelonephritic changes within the multicystic dysplastic kidney.
The patient was discharged in good health on the ninth post-operative day and had remained symptom free after 3 years follow-up period.
Figure 1:
Patient's abdomen preoperatively
Figure 2:
Intra-operative findings of dysplastic left half, the isthmus and normal right half
Footnotes
Competing Interests: The authors have declared that no competing interests exist.
Grant support: None
References
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