Unilateral Renal Agenesis with Compensatory Hypertrophy Presenting as Recurrent Abdominal Pain and Misinterpreted Functional Disorder in Late Childhood

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Description

A twelve-year-old boy was referred to a pediatric urology service after repeated episodes of vague abdominal pain over nearly one year. The discomfort was intermittent, mostly located in the left lower abdomen, and occasionally associated with fatigue after physical activity. The child had been evaluated multiple times in primary care settings, where symptoms were attributed to gastrointestinal sensitivity and functional abdominal discomfort because routine laboratory tests and basic abdominal ultrasonography reports were interpreted as unremarkable. The patient’s prenatal and perinatal history was largely uneventful, although detailed antenatal imaging records were not available due to relocation of the family during pregnancy. Growth and developmental milestones were appropriate for age. There was no history of urinary incontinence, dysuria, or prior documented urinary tract infection. Blood pressure recordings in community clinics were occasionally borderline elevated but not consistently monitored.

On physical examination at presentation, the child appeared healthy with mild discomfort on deep palpation of the left flank region. No palpable abdominal mass was identified. External genital examination was normal. No spinal or lower limb abnormalities were present. Blood pressure measured in the clinic was mildly elevated for age percentile but repeated readings showed variability. Laboratory evaluation revealed normal serum creatinine, normal electrolytes, and absence of inflammatory markers. Urinalysis showed no hematuria, pyuria, or proteinuria. Because of persistent symptoms without clear explanation, a repeat detailed renal and urinary tract ultrasound was performed with attention to renal asymmetry.

Ultrasonography demonstrated absence of the right kidney in the renal fossa and no identifiable ectopic renal tissue along the expected embryologic migration pathway. The left kidney was significantly enlarged, measuring above the expected size for age, with increased cortical thickness consistent with compensatory hypertrophy. No hydronephrosis, cystic lesions, or focal masses were observed. Doppler evaluation demonstrated preserved renal perfusion with increased vascular flow consistent with adaptive hyperfiltration.

To confirm anatomy and exclude ectopic renal tissue, magnetic resonance urography was performed. This confirmed complete absence of the right kidney and ureteral bud formation on that side. The left kidney showed normal collecting system architecture with no obstruction. The urinary bladder appeared normal in morphology and capacity. No associated Müllerian or Wolffian duct anomalies were identified.

A radionuclide renal scan was subsequently performed to assess functional distribution. The scan demonstrated solitary renal function exclusively in the left kidney with preserved global filtration but increased single-kidney workload. No uptake was seen in the right renal fossa or ectopic locations. These findings established the diagnosis of unilateral renal agenesis with compensatory hypertrophy of the contralateral kidney.

After diagnosis, a detailed review of the patient’s symptoms suggested that intermittent abdominal discomfort was likely related to increase renal perfusion demands and possible musculoskeletal strain rather than intrinsic gastrointestinal disease. The absence of urinary symptoms had contributed to delayed recognition, as the child had adapted well physiologically to single-kidney function.

Blood pressure monitoring was repeated using ambulatory assessment, revealing intermittent elevations consistent with early adaptive renal hemodynamic changes. Although renal function remained normal, the increased workload on the solitary kidney raised concern for long-term susceptibility to hyperfiltration-related injury. Management focused on surveillance and preventive strategies rather than surgical intervention. The patient and family were counseled regarding the presence of a single functioning kidney and the importance of avoiding dehydration, nephrotoxic medications, and high-risk contact sports without protective measures. Regular follow-up was arranged for blood pressure monitoring, renal function assessment, and periodic imaging to evaluate kidney growth and structural integrity.

Clinical presentation in childhood may be subtle, and symptoms are often absent until incidental discovery. When present, nonspecific abdominal or flank discomfort may lead to misinterpretation as functional gastrointestinal disorders, as occurred in this patient. Lack of early detailed imaging review contributed to delayed recognition of the underlying anatomical condition. Although a solitary kidney can maintain normal function throughout life, long-term risks include systemic hypertension, proteinuria, and gradual decline in renal reserve due to adaptive hyperfiltration. Early identification is therefore important for structured monitoring and prevention of secondary renal injury. Regular follow-up allows early detection of functional decline and implementation of protective strategies.

Imaging plays a central role in diagnosis. Ultrasonography is often the first modality, but its accuracy depends on operator experience and thorough evaluation of renal fossa and ectopic locations. Magnetic resonance urography provides superior anatomical delineation without radiation exposure, particularly useful in pediatric patients. Nuclear renal scanning confirms functional distribution and excludes ectopic functioning tissue. Management does not typically involve surgical correction, but rather long-term surveillance and patient education. Avoidance of unnecessary medication exposure that may affect renal function is essential.

Conclusion

This case highlights a late diagnosis of unilateral renal agenesis presenting with recurrent abdominal discomfort in a school-aged child. Recognition of compensatory renal hypertrophy and appropriate imaging interpretation allowed accurate diagnosis and elimination of unnecessary repeated investigations. Structured follow-up and preventive counseling ensured preservation of renal health and stabilization of symptoms during observation. Counseling regarding hydration status during illness or physical exertion helps reduce risk of acute kidney injury.