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Child Health Guideline Identifier

Renal - single, multi-cystic dysplastic and duplex kidneys

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This guideline describes recommended investigation and follow up for children with a single kidney, multicystic dysplastic kidneys, or a duplex collecting system.

Investigation tips

  • Renal USS: Include child's growth centiles on USS request so normed renal volumes can also be reported
  • Urinalysis: assess albuminuria/ proteinuria on early morning samples.
  • Blood pressure: If concern about hypertension consider ambulatory blood pressure monitoring. If this is unavailable or the child is too young, consider serial blood pressure measurements in day stay or ward over several hours.
  • Online Estimated GFR caclulator available here:
  • Online Multivariable Pediatric Renal Nomogram (for expected renal size) available here:

Single kidney

Single kidney is usually found antenatally, or can follow nephrectomy. Most common findings include unilateral renal agenesis, or a contralateral multicystic dysplastic kidney. 

Around one in 1500 children will have congenital absence of one kidney. The majority will have normal overall renal function but have an increased risk of hypertension and albuminuria/proteinuria from hyperfiltration.

Confirm antenatal findings with a postnatal scan. Sometimes a pelvic kidney may be identified on postnatal scan The normal course for a single kidney is to grow rapidly to compensate, and the aim of imaging is to ensure that this occurs and is maintained as the child grows.

Identification of children with single kidney at increased risk of developing Chronic Kidney Disease (CKD)

  •  Low birth weight infants who are are at risk of reduced nephron mass from birth.
  • Insufficient growth of the functioning kidney. Generally this would be expected to reach the 90th centile for height and weight within the first year. This may be assessed via centiles available in radiology and on line via nomogram, for example:
  • Children who have an episode of acute kidney injury.
  • Around one third will have an associated urological abnormality which may cause additional renal issues
  • If associated with another condition in which the evolving disease/syndrome may lead to renal insufficiency
  • Long term raised BMI has been shown to increase the risk of earlier onset of albuminuria.
  • The adolescent growth spurt may be a critical time for these children and if being followed by GP highlight the need for follow up at this time. 

Recommended follow-up schedules for single kidney

Standard follow-up (no increased risk factors, no renal insufficiency, no hypertension, no proteinuria) Follow-up for increased risk factors Follow up for renal insufficiency +/- proteinuria +/- hypertension
  1.  USS at 3 months, one year and every 5 years thereafter until 15-16 years old / growth completed. 
  2. Blood Pressure and check for albuminuria/ proteinuria annually throughout childhood and adolescence This can be done in primary care (with appropriate BP measuring equipment for children).
  3. Check creatinine and estimated GFR (height (cm)/creatinine x 36.5) every five years (eg at age 5, 10 and 15).
  1.  USS at 3 months, 12 months, and then based on clinical indication (if kidney is small every 2-3 years) and if other indicators of renal insufficiency develop manage as per 3.
  2. Consider monitoring blood pressure and for proteinuria/ albuminuria 6 monthly during periods of increased risk identified 
  3. Check BP and urine for albuminuria/ proteinuria 6-12 monthly
  4. Check creatinine and estimated GFR every 5 years.
  1. Check BP and urine for albuminura/ proteinuria every 3-6 months depending on the severity and need to start treatment. 
  2. Recommend discussion with nephrology (+/- referral), to clarify required management and continued frequency of follow-up.

Multicystic Dysplastic Kidney

The incidence of Multicystic Dysplastic Kidney (MCDK) is around 1 in 4000 births.

One kidney consists of non communicating cysts with non-functioning parenchyma between them, leaving the child with effectively one functioning kidney, which may have associated urological abnormalities (eg vesico-ureteric reflux, PUJ configuration).

Differential includes cystic dysplasia (functioning but abnormal structurally) and severe pelvi-ureteric junction obstruction.

Recommended follow-up schedule for multicystic dysplastic kidney

  1. Ultrasound as per single kidney follow up. This is to:
    1. Assess for compensatory hypertrophy in the remaining kidney and any other abnormalities.
    2. Look for involution of the MCDK (~60% will completely involute, majority within 3 years, less likely if >5cm). Failure to involute is no longer always an indication for surgical removal, however it may be associated with an increased risk of developing CKD in the remaining contralateral kidney. 
  2. Nuclear medicine imaging can help to confirm diagnosis if the ultrasound appearance is unclear.
  3. MCU not required in otherwise asymptomatic child with appropriate compensatory hypertrophy of the contralateral kidney
  4. Blood pressure and proteinuria monitoring as per single kidney.

Duplex kidney

Duplex kidneys are kidneys in which the collecting system may be wholly or partially duplicated, making the kidney appear bigger than normal. They occur in about 1% of the population and are of no clinical significance in the majority of children. 

If diagnosed antenatally suggest follow up postnatal USS at 3 months to determine whether duplex is uncomplicated or complicated. In the assessment of whether a duplex is uncomplicated the important considerations are:

  • Presence of dilatation - calyceal or ureteric
  • Presence of dysplasia or atrophy.
  • Assessment of bladder to ensure normal bladder, no ureterocele, and no pelvic cyst.

Recommended follow-up schedule for duplex kidney

  • If there is no dilatation and no atrophy/dysplasia (i.e. uncomplicated duplex) the kidney is essentially normal and no further follow up required. 
  • If dilatation present, factors to consider are upper pole versus lower pole, and presence/absence of a dilated ureter:
    • Lower pole, no dilated ureter - follow the National antenatal renal dilation guideline
    • Lower pole, dilated ureter - provisional diagnosis is VUR, manage as per symptoms.
    • Upper pole, no dilated ureter - refer for Renal MDM (multidisciplinary renal/urology meeting, or local equivalent) for imaging review -likely to observe along  National antenatal renal dilation guideline
    • Upper pole, dilated ureter - provisional diagnosis VUJ obstruction +/- ectopic ureter, refer for Renal MDM/ local equivalent imaging review.
  • If dysplasia/atrophy present needs DTPA and Renal MDM imaging review (or local equivalent). Ensure clinical detail on DTPA request includes duplex kidney.
  • If ureterocele present and dilation - refer to paediatric urology/surgery
  • If ureterocele present, small and no dilation - repeat USS at 3-6 months, if no change - no further follow up required
  • Girls with a duplex kidney, once toilet trained, should be completely dry between voiding. If not, there may be an ectopic ureter - refer to paediatric urology/surgery.

Advice regarding physical activity/sport

The American Academy of Paediatrics now recommends no restrictions. There has been no evidence in large studies to support sporting restriction. The number of renal injuries due to sporting accidents is far fewer than injuries (e.g. head, spine and limb injuries). Renal injuries from motor vehicle accidents are much more common than renal injuries from sports activities. The Canadian urological association has published useful recommendations and information for counselling caregivers:

Information for families


  1. Growth and function in childhood of a normal solitary kidney from birth and from early infancy. Paediatr Nephrol 2014 29; 249-256.
  2. Clinical implication of the solitary functioning kidney. Clin J Am Soc Nephrol 2014 9: 978-986.
  3. Sport related Kidney Injury among High School athletes. Paediatrics July 2012
  4. Sports and the solitary kidney: What parents of a young child with a solitary kidney should know. Can Urol Assoc J 2014;8(7-8):233-5.
  5. Unilateral multicystic dysplastic kidney: long term outcomes Arch Dis Child. 2006 Oct; 91(10): 820-823.
  6. Management and etiology of the unilateral multicystic dysplastic kidney: a review. Pediatr Nephrol. 2009 Feb;24(2):233-41.

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Document Control

  • Date last published: 22 February 2018
  • Document type: Clinical Guideline
  • Services responsible: Paediatric Nephrology
  • Author(s): Tonya Kara, Neil Price
  • Editor: Greg Williams
  • Review frequency: 2 years

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