Renal Cysts in the Pediatric Population: When to Operate Maahum Haider Seattle Children’s Hospital General Surgery

Introduction The kidney is one of the most common sites in the body for cysts Renal cysts in children can be associated with normally functioning kidneys, or they can be the result of serious genetic abnormalities as part of a syndrome, sometimes resulting in ESRD The decision to operate depends on symptoms, prognosis and underlying cause and is aided by radiological studies; most commonly ultrasound and CT

Cystic Diseases of the Kidney Non-heritable Heritable Simple cysts Acquired Renal Cystic disease Multicystic dysplastic kidneys Sporadic glomerulocystic disease Spectrum of multilocular cysts ARPKD ADPKD Nephronopthisis Medullary cystic disease Congenital nephrosis Familial hypoplastic glomerulocystic disease Multiple malformation syndromes Tuberous sclerosis, VHL

Bosniak Classification Category I Simple benign cyst with (1) good through-transmission (i.e., acoustic enhancement), (2) no echoes within the cyst, (3) sharply, marginated smooth wall; requires no surgery. Category II Looks benign with some radiologic concerns including septation, minimal calcification, and high density; requires no surgery. Category IIF Although calcification in wall of cyst may even be thicker and more nodular than in category II, the septa have minimal enhancement, especially those with calcium; requires no surgery. Category III More complicated lesion that cannot confidently be distinguished from malignancy, having more calcification, more prominent septation of a thicker wall than a category II lesion; more likely to be benign than malignant; requires surgical exploration and/or removal. Category IV Clearly a malignant lesion with large cystic components, irregular margins; solid vascular elements; requires surgical removal. Campbell-Walsh, 9th Ed.

Simple Cysts Very rare in pediatric population (0.22%) Most arise from nephrons and collecting ducts (widened area, diverticulum or isolated sac) Often found incidentally in association with other urinary tract anomalies If symptomatic, presenting features may include abdominal pain, hematuria, or obstruction from peri-pelvic cysts Ultrasound is diagnostic test of choice. If indeterminate, CT with IV contrast is the next step

Simple Cysts Should not be overlooked as they may be an early presentation of ADPKD Most can be managed conservatively with US follow up If patient is symptomatic, cysts can be aspirated and injected with sclerosant to prevent re-accumulation Recalcitrant cysts can be treated with percutaneous resection, intrarenal marsupialization or laparoscopic unroofing

Acquired Renal Cysts Found to be a feature of ESRD Duration of dialysis is directly proportional to number and size of cysts Successful transplantation often results in regression of the cysts If cyst is infected, percutaneous drainage may be considered If heparinization for dialysis is associated with significant hematuria, embolization or nephrectomy may be indicated

Multicystic Dysplastic Kidney Most frequent cystic disease in newborn Renal maldevelopment with diffuse cysts: “bunch of grapes” appearance on US Often associated with abnormalities of contralateral urinary tract (UPJ obstruction, VUR) Prophylactic nephrectomy has been suggested to avoid malignant transformation but this is very rare (1:2000) Long term follow up with US shows that most become smaller or stay the same size. Very few enlarge and it is up to the surgeon’s discretion to remove it

Multilocular cysts Represent a spectrum of conditions that has been described as a continuum in children: Cystic nephroma Cystic partially differentiated nephroblastoma Multilocular cyst with nodules of Wilms Cystic Wilms Qualify as complex renal cysts on CT, suspicious for malignancy (Bosniak III-IV)

Multilocular Cysts Two main operative concerns: Is the contralateral urinary tract normal? Is the abnormal kidney involved with Wilms’ tumor? Currently no reliable means of ruling out malignancy without histopathology and therefore warrants nephrectomy If enucleation or partial nephrectomy is chosen, recurrence is possible

Conclusions There are many different etiologies of renal cysts Some can simply be observed and go by unnoticed, while others require surgical intervention and extensive medical management The Bosniak classification aids in determining which cysts can be managed expectantly and which require surgical exploration or excision Main operative considerations include patient’s symptoms, natural history of disease process, and abnormalities in contralateral urinary tract that may need to be addressed or repaired prior to surgery

References Management of simple renal cysts in children G.V.S. MURTHI, A.F. AZMY and A.G. WILKINSON* Departments of Paediatric Surgery and *Paediatric Radiology, Royal Hospital for Sick Children, Glasgow G3 8SJ, UK Current Diagnosis and Treatment: Surgery Chapter 43. Pediatric Surgery Simple Renal Cysts in Children P G Ransley FRCS The Hospital for Sick Children, London Campbell-Walsh Urology Section XVII: Pediatric Urology