Management of simple renal cysts in children

Departments of Paediatric Surgery and *Paediatric Radiology, Royal Hospital for Sick Children, Glasgow G3 8SJ, UK

Simple renal cysts are uncommon in children and their presentation and management has changed with increasing use of ultrasound scans. The aim of this study was to review our experience and highlight some peculiarities in diagnosis and management of these cases. Eight cases were diagnosed and two symptomatic cases underwent aspiration under ultrasound guidance; one case recurred and required re-aspiration. Differentiation of simple renal cysts from other cystic lesions of the kidney, aspiration of symptomatic cysts and the importance of long-term follow-up are discussed.

Simple renal cysts (Figure 1), although common in adults, are rare in children.^1-3 They are usually asymptomatic and are discovered incidentally during investigation for other urinary tract symptoms. The diagnosis of a simple renal cyst is made on the basis of typical radiological findings with surrounding normal renal parenchyma, normal renal function and no associated systemic illnesses or disorders. Aspiration under ultrasound guidance and injection of sclerosant is an established method of treatment of such symptomatic cysts in adults’.⁴ We present eight cases of simple renal cysts in children. Two underwent aspiration to relieve cyst-related pain. The indications for and methods of aspiration under ultrasound guidance are dealt with in this article.

Eight cases of simple renal cysts were diagnosed at the Royal Hospital for Sick Children, Glasgow, Scotland, between the period of January 1993 to December 1997. Their case notes and radiological investigations were reviewed and data collected regarding patient characteristics, symptomatology, features of renal cysts, associated renal pathology and treatment modalities employed. Ultrasound examination was the initial diagnostic study in all cases except one patient where the lesion was detected on an intravenous urogram (IVU). Computerised tomography (CT) scans were performed to further delineate the lesion in one patient and contrast injection was undertaken in a recurrent cyst. Patients with abnormal renal function, polycystic or cystic dysplastic kidneys or disorders that could possibly account for the presence of cysts (tuberous sclerosis, previous malignancy) were excluded from the study.

Figure 1: Longitudinal ultrasound scan of the kidney showing simple renal cyst

All eight cases met the established radiological and clinical criteria for the diagnosis of a simple renal cyst. Renal function was normal in all cases and no child had hypertension. Aspiration under ultrasound guidance and local anaesthesia was attempted in two patients who were considered to have cyst-related recurrent loin pain. The essential features of the two cases that underwent aspiration are highlighted and all eight cases are summarised in Table 1.

Case 1: An 11 year-old-girl presented with a 3-month history of recurrent right loin pain. Ultrasound showed a simple cyst measuring 4.9 cm in diameter in the right kidney in a para pelvic location. There was associated mild hydronephrosis (Figure 2) and the rest of the renal parenchyma and the opposite kidney were normal. Aspiration under ultrasound guidance to relieve the symptoms was performed. This procedure was initially attempted under local anaesthesia but abandoned as the patient could not tolerate it and was performed successfully under general anaesthesia.

Case 2: A 12-year-old girl presented with loin pain and ultra-sound examination revealed a cyst measuring 2.4 cm in diameter in the parenchyma of a horse-shoe kidney. This cyst was successfully aspirated under local anaesthesia with resolution of symptoms. Symptoms of loin pain recurred after 18 months and ultrasound scans demonstrated the cyst had refilled to a diameter of 2.5 cms. Cyst puncture and contrast injection was performed to determine whether it was safe to inject sclerosant. Contrast flowed into lymphatic channels (Figure 3), and it was decided not to inject sclerosant for fear of damaging the lymphatics. The cyst was aspirated to relieve the pain. It has since refilled but repeat aspiration for a third time was not performed, as the child was asymptomatic.

No	Sex	Age of presentation (years)	Presenting symptoms	Size*	Associated	Treatment pathology
1	F	11	Loin pain	4.9cm	Mild hydronephrosis	Aspiration x1
2	F	12	Loin pain	2.4cm	Horseshoe kidney	Aspiration x2
3	F	5	Enuresis	--#	Meatal stenosis	Observation
4	F	10 months	Haematuria	2.3cm	Nil	Observation
5	F	3	UTI*	1.2cm	Nil	Observation
6	M	3	Proteinuria	1.2cm	Family history of polycystic kidneys	Observation
7	F	3	UTI	1.9cm	Nil	Observation
8	F	12	UTI	1.2cm	Nil	Observation

*Maximum diameter on ultrasound before aspiration; #diagnosed on IVU; †urinary tract infection. All eight cases are being followed up (range 1 - 5 years) with regular renal ultrasound scans and remain asymptomatic

The presentation of simple renal cysts has changed from the presence of an abdominal mass to most cases currently being detected on ultrasound scanning, either routinely (ante-natal) or for other renal or abdominal pathology.⁵ Previously, IVU used to be the initial diagnostic study in the evaluation of a renal cyst and surgical exploration was often undertaken to confirm the diagnosis of a simple cyst.6 Sonographic features of a simple renal cyst are defined as a round, smooth-walled mass with no internal echoes and causes distal echo-enhancement. ^3,6 As the ultrasonic definition of simple renal cysts is well established, further investigations in the form of IVU, CT scan, contrast injection or surgical exploration is less commonly undertaken in modern practice. Normal renal function and the absence of other renal pathology (polycystic disease, cystic dilatation in the upper pole of a duplex kidney, calyceal diverticulum, abscess or a cystic mass), however, must be confirmed before making the diagnosis of a simple renal cyst. If the diagnosis cannot be established with certainty on the basis of an ultrasound scan, IVU or CT scans are undertaken to further delineate the renal parenchyma. An intravenous urogram is especially useful in differentiating a calyceal diverticulum or cystic dilatation of the upper pole of a duplex kidney from a simple cyst. Similarly, well known associations such tuberous sclerosis should be considered in the differential diagnosis. The association of simple renal cysts with AIDS has been described.⁷

Previously, symptomatic cysts were treated by deroofing or excision.8 We reserve aspiration under ultrasound guidance for simple cysts that cause loin pain. Aspiration of symptomatic cysts in adults is common practice and there are reports of cyst aspiration and injection with sclerosants, such as alcohol and hypertonic saline, to prevent re-accumulation. ^4,9,10

In our series, the two largest cysts caused pain that responded to aspiration under ultrasound guidance. Aspiration should also be undertaken if the cyst is causing local pressure effects; one patient (Case 1) who had aspiration had a parapelvic cyst that was causing pain and also mild hydronephrosis. Others have reported this. ¹¹

In summary, we would like to highlight a number of aspects pertaining to simple renal cysts. Firstly, most cases are asymptomatic and are best treated conservatively by regular ultrasound follow-up.
Where aspiration is being considered, both clinical symptoms and radiological features need to be considered. There is perhaps a case for injecting contrast into all symptomatic cysts prior to sclerotherapy especially in children where associated congenital pathology such as lymphangiomatous cysts is more likely. Secondly, re-accumulation of cyst fluid following aspiration is not uncommon and further treatment in such cases should be based on the symptoms. ^12,13

In children, aspiration under sedation or general anaesthesia should be considered, especially in the anxious child who does not co-operate. Lastly, as the natural history of simple cysts is not known, long-term sonographic follow-up is recommended; simple cysts can be the initial manifestation of autosomal dominant polycystic disease in a child.^3,12

Figure 3: Contrast injection (IO hexol) showing cyst draining in to local lymphatics

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Copyright date: 24th January 2001
Correspondence: Mr AF Azmy, Department of Paediatric Surgery, Royal Hospital for Sick Children, Glasgow G3 8SJ, UK