Surgical Renal Conditions: Role of Imaging Modalities

Introduction

A wide variety of pediatric nephro-urological conditions can be diagnosed and evaluated by various imaging modalities present nowadays to understand complex anatomy and functional status. Some of the pediatric renal conditions require surgical intervention at an appropriate time to eliminate/alleviate the symptoms and improve the function of the nephron-urological system. Pelvic-ureteric junction obstruction (PUJO) is one of the most common causes of congenital urinary tract obstruction,[12] presenting in one in seven cases of antenatally detected hydronephrosis.[34] Most common etiology contributing to PUJ obstruction is intrinsic obstruction due to an adynamic stenotic segment, accounting for nearly three-fourths of the total cases.[5] The major challenge in the management of PUJO is to decide which of these pediatric patients, who are mostly asymptomatic, require a pyeloplasty[67] to relieve the obstruction as the hydronephrosis in two-thirds of children with PUJO spontaneously improves over time and hence do not need surgery. Ultrasonography (USG) and serial renal dynamic scintigraphy (RDS) are currently utilized to tailor the surgical management of PUJO.

Another most common urological anomaly in children is vesicoureteric reflux (VUR), which is the retrograde passage of urine from the bladder into the upper urinary system. Most of the cases are medically managed with continuous antibiotic prophylaxis (CAP); however, surgery is the treatment of choice in cases with recurrent urinary tract infection (UTI) despite CAP, high-grade VUR reflux, less probability of spontaneous resolution, and reflux nephropathy. Radionuclide cystography (RNC) and micturating cystourethrography (MCU) are the imaging modalities for the evaluation of VUR.[89]

Congenital renal anomalies such as ectopic kidneys, duplex kidneys, horseshoe kidneys, crossed fused kidneys, and multi-cystic dysplastic kidneys are a major subgroup of pediatric renal disease that requires special attention in case of symptomatic and deranged function as the anatomy is challenging.

Radiological modalities such as USG, fluoroscopic micturating cystogram (MCUG), magnetic resonance urography (MRU), and occasionally computed tomography (CT) urography, along with radionuclide scintigraphy including L, L, ethylenedicysteine (Tc-99m-LLEC), or Tc-99m-diethylenetriaminepentaacetic acid dynamic renal scintigraphy, dimercaptosuccinic acid (Tc-99m-DMSA) renal scintigraphy, and radionuclide micturating cystography (direct and indirect RNC), contribute to a holistic morphofunctional assessment in the above-mentioned renal diseases for surgical management.

Discussion

The first case shows a 1-year-old baby with antenatally detected right-sided hydronephrosis; a combination of MCU, USG, and RDS was crucial for diagnosing PUJO.[10] This case demonstrated the use of RDS in confirming the PUJO along with the assessment of the renal function [Figure 1]. The second case demonstrated the use of USG and RDS in a 3-year-old postureteric reimplantation patient, emphasizing the importance of imaging in postoperative management.[11] Well-tempered renogram helped in quenching the diagnosis of right vesicoureteric junction obstruction noninvasively and concorded with the USG finding of right renal hydronephrosis [Figure 2].

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Figure 1 Case 1: A 1-year-old baby with antenatally detected right-sided hydronephrosis asymptomatic after birth with no history of lump/pain in abdomen/fever or recurrent urinary tract infection. The baby voids normally in stream, with no complaints of dribbling or straining of urine. Per abdominal findings are soft, nondistended, no organomegaly with positive bowel sounds. Micturating cystourethrography (MCU) shows opacification of the right ureter likely due to right vesicoureteric reflux (a). Ultrasonography of the patient shows right-sided hydronephrosis, (b) first-row images. The baby underwent renal dynamic scintigraphy, which showed a hydronephrotic right kidney with progressive accumulation of radiotracer (c) in the dilated pelvic calyceal system with no significant clearance in the prevoid (e) and delayed (f) static images with preserved function of 54% (d). Overall renal dynamic scintigraphy findings were suggestive of right pelvic-ureteric junction obstruction

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Figure 2 Case 2: A 3-year-old patient who is a known case of left vesicoureteric junction obstruction (VUJO) has undergone left lead-better politano ureteric reimplantation with Hendren’s tapering in 2019 and presented to the outpatient department with mild abdominal pain. On examination, suprapubic scar was well-healed and there was no lump or abdominal distension. Well-tempered renal dynamic scintigraphy (a) of the patient shows an enlarged and hydronephrotic right kidney with visualization of the ureter in the delayed static images and a rising renogram curve, suggestive of right-sided obstruction at the level of vesicoureteric junction. The ultrasonography (b) of the patient showed right hydronephrosis with dilated right ureter with suspicious for right VUJO

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Regarding the third case, a 10-month-old baby with left hydronephrosis and percutaneous nephrostomy (PCN) insertion, USG and nephrostogram provided insights into the condition and confirmed proper PCN placement.[12] RDS helped determine the function of the affected left kidney with the assessment of drainage pattern through PCN and physiological by the use of clamping the PCN and then acquiring static image after declamping the PCN [Figure 3]. For the fourth case imaging (USG, intravenous pyelogram, contrast-enhanced CT, and RDS) in a 10-year-old diagnosed severely hydronephrotic right kidney, guiding treatment decisions.[13] RDS helped in determining the split function of the kidneys, thereby helping in clinical decision-making for consideration of right kidney nephrectomy [Figure 4].

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Figure 3 Case 3: A 10-month-old baby with antenatally diagnosed left hydronephrosis with left percutaneous nephrostomy (PCN) insertion. Ultrasonography (a) shows left moderate–severe hydronephrosis with PCN noted in situ. There was no history of fever/lump or pain in the abdomen/vomiting/dysuria. Nephrostogram (b) of the patient showed the proper positioning of PCN tube in the left kidney with drainage of the contrast through the ureter to the bladder. Renal dynamic scintigraphy (c and d) of the patient shows a hydronephrotic left kidney with preserved function (48%) and delayed clearance, majorly draining through the normal pathway

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Figure 4 Case 4: A 10-year-old boy presented with right upper quadrant pain for 1 year on and off episodes with recurrent episodes of documented urinary tract infection, not associated with fever, vomiting, dribbling, and hematuria. Per abdominal examination shows a nontender, nonmobile firm mass palpable in the right lumbar region measuring 5 cm × 5 cm. Ultrasonography (a) shows moderate–severe hydronephrosis of the right kidney with normal-sized left kidney with no hydronephrosis. (b) Renal dynamic scintigraphy of the patient showed an enlarged left kidney with preserved function and nonobstructive clearance with nonvisualized/nonfunctioning right kidney. (c) Intravenous pyelogram of the patient shows nonvisualization of the right kidney and ureter with mild dilatation of the left pelvicalyceal system, with the left ureter showing normal course and caliber with no intraluminal filling defect. (d) Contrast-enhanced computed tomography of the patient showed a severely hydronephrotic right kidney with ballooned out pelvis with normal left kidney

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In the fifth case, RDS, MRU, and MCU contributed to the diagnosis of the right duplex pelvicalyceal system in a 5-year-old baby with abdominal pain and recurrent UTIs.[14] RDS can determine the function and clearance pattern of individual moieties in a duplex kidney [Figure 5]. The sixth case described a 12-year-old with left renal calculi and subsequent PUJO, for which imaging (USG, nephrostogram, CT kidney, ureter, and bladder, MRU, and RDS) played a crucial role in assessing the duplex kidney and guiding intervention decisions.[15] RDS diagnosed a nonfunctioning lower moiety of the left kidney, thereby helping in further management of the patient [Figure 6]. For the seventh case, imaging (USG and CT urography) revealed a horseshoe kidney in a 17-year-old patient with continuous urinary dribbling since birth, showcasing the importance of imaging in anatomical abnormalities. Horseshoe is usually associated with genitourinary malformation and can develop a number of complications such as renal calculi, hydronephrosis, and PUJO, due to poor drainage. CT urography and USG help in the diagnosis of the horseshoe kidney. CT urography usually helps in the identification of calculi/blockages. It shows enhancement and excretory phase helps to assess the collecting system.[16] RDS helps in determining the function and drainage pattern of each moiety as depicted in our case. Furthermore, it is a very useful modality to distinguish genuine obstruction from passively dilated systems and contribute to diagnosing PUJ obstructions evidently. Furthermore, it can best demonstrate the presence of functioning parenchymal tissue in the isthmus consists of.[17] As horseshoe kidneys are prone to vesicoureteral reflux, MCU is usually performed as in our case [Figure 7].[18]

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Figure 5 Case 5: A 5-year-old baby with right-sided abdominal pain and recurrent urinary tract infection for 3 months was diagnosed with right duplex pelvicalyceal system and duplex ureter. (a) Renal dynamic scintigraphy of the patient shows a right-sided duplex system with preserved functioning upper moiety and impaired functioning lower moiety. (b) Magnetic resonance urography of the patient shows duplex moieties of the right kidney. (c) MCU of the patient reveals right-sided vesicoureteric reflux with right duplex system and severe dilatation of the right pelvicalyceal system

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Figure 6 Case 6: A 12-year-old female child with complaints of left flank pain 3 years ago was diagnosed with left renal calculi and underwent left percutaneous nephrostomy (PCN) insertion. However, in the last 3 months, there was severe left flank pain and later on was diagnosed as left pelvic-ureteric junction obstruction, for which the child underwent left pyeloplasty with a double-J (DJ) stent. Subsequently, the patient developed recurrent pus discharge from the left flank and thereby underwent left DJ stent exchange with retrograde pyelogram and left PCN insertion. The patient has current drainage of 200–300 mL/day through the left PCN along with per urethral excretion also. On examination, per abdomen was soft with no lump and with a healthy scar. (a) Ultrasonography of the patient showed hydronephrosis of the left kidney with normal size, morphology, and attenuation of the right kidney. (b) Nephrostogram of the patient shows adequate drainage of the contrast into the bladder with intact left-sided PCN in situ. (c) Computed tomography kidney, ureter, and bladder of the patient showed dilatation of the mid and lower pole of the left kidney with DJ stent in situ. For better understanding of the anatomy. (d) Magnetic resonance urography was done and it showed upper and lower moiety of the left kidney, suggestive of left duplex kidney with DJ stent noted in situ. (e) Renal dynamic scintigraphy of the child shows a duplex left kidney with hydronephrotic upper moiety with preserved function and delayed clearance along with nonfunctioning lower moiety. The right kidney shows normal function with nonobstructive clearance

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Figure 7 Case 7: A 17-year-old complaints of continuous urinary dribbling since birth, with no dry period and never passes in stream. (a) Ultrasonography showed a fused mass in midline (horseshoe kidney) with single right ureter with orthotopic opening at the right vesicoureteric junction (VUJ). Left renal moiety shows dilated ureter terminating in the wall of the vagina with another small nondilated ureter cranial to dilated ureter on the left side but no ureteric opening at left VUJ, likely suggestive of partial duplication. (b) Subsequent MCU showing no vesicoureteric reflux. (c) Computed tomography urography of the patient showed fused renal parenchyma in the midline. The patient underwent a renal dynamic scintigraphy scan to assess the split function of both the moieties. (d) Renal dynamic scintigraphy of the patient showed preserved functioning left moiety and mildly impaired functioning right renal moiety with nonobstructive clearance

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The eighth case demonstrated an 8-year-old patient with right-to-left crossed fused ectopia, and imaging (contrast-enhanced magnetic resonance imaging [MRI], RDS, and nephrostogram) aided in assessing renal function and guiding management decisions. Crossed fused renal ectopia is the second-most common fusion anomaly after horseshoe kidney, with 85%–90% of the patients showing partial or complete fusion.[19] Unlike in our case, left-to-right ectopia is most common. Crossed fused ectopia generally shows complications such as hydronephrosis, recurrent UTIs, and renal calculi. Due to aberrant vascular anatomy, the crossed ectopic kidney generally demonstrates a decreased function.[2021] Similarly, in our case, we demonstrate a crossed ectopic left kidney with hydronephrosis and impaired function as shown in RDS of the patient, which usually helps in the assessment of the function of each moiety and drainage pattern (obstructive or nonobstructive). Similar to USG, MRI can demonstrate anatomical details in a better and excellent way.[22] As there is a PCN tube inserted into the left renal moiety, nephrostogram is also performed to assess the tube position [Figure 8]. For the ninth case, imaging (USG, MCU, MR urography, RDS, and DMSA) played a pivotal role in diagnosing ureterocele-related hydronephrosis and assessing renal function in an 8-year-old patient with intermittent flank pain. Ureterocele is a congenital condition that presents as an abnormal dilatation of the distal ureter into the bladder. Like it is demonstrated in our case of the right ureterocele, cobra head appearance of the distal ureter as the distal ureter balloons at its opening into the bladder, forming a sac-like pouch, is a typical finding noted in USG.[23] Furthermore, we noted an oval-shaped defect was noted in the right-sided trigone in the MCU scan. MRU serves as a valuable additional tool for assessing ureteroceles and associated anomalies in the urinary tract with precise anatomical and vascular information along with renal function. Even though there is less radiation exposure, it is usually an expensive imaging modality.[24] Renal dynamic scan using 99m Tc-LLEC can provide valuable information that provides insights into the differential kidney function and helps confirm or rule out any obstruction as depicted in our case [Figure 9].[25] The tenth case showed a 16-year-old patient with bladder exstrophy and VUR, and imaging (USG, MCU, and DMSA) was essential for planning gastric neobladder surgery while considering renal function and complications. MCU is the primary and gold standard investigation to detect VUR.[26] In our case, we demonstrated a bilateral Grade 5 VUR on MCU, with USG of the patient showing bilateral hydroureteronephrosis. VUR can lead to recurrent UTI and subsequently to renal scarring, also called reflux nephropathy, as depicted in the DMSA scan of the patient [Figure 10]. For the 11^th case, RDS was employed to assess the function of transplanted kidneys in a 16-year-old patient with chronic kidney disease Grade 5 who underwent a double renal transplant. Posttransplant renal scintigraphy has been shown to provide insights into the perfusion, functioning, and drainage pattern of the transplanted kidney for better management of postrenal transplant complications [Figure 11]. The 12^th case showed a 16-year-old female with suspected renal anomalies, RDS and single-photon emission computed tomography/CT aided in localizing the left kidney and assessing its functional status which was not visualized by USG [Figure 12]. This discussion underscores the pivotal role of various imaging modalities in diagnosing and managing a spectrum of surgical renal conditions in pediatric patients.

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Figure 8 Case 8: A 8-year-old male child with complaints of pain in umbilical and left lumbar regions (on and off) for 2 years with normal urine stream and no history of urinary tract infection was diagnosed with right-to-left crossed fused ectopia with left hydronephrosis. He underwent cystoscopy with left flank exploration and left percutaneous nephrostomy (PCN) placement. (a) Renal dynamic scintigraphy of the patient reveals mildly impaired functioning and hydronephrotic left renal moiety (40%) with delayed nonobstructive clearance with crossed fused right renal moiety with preserved function and nonobstructive clearance (60%). (b) Contrast-enhanced magnetic resonance imaging of the child shows enhancing right-to-left crossed fused ectopia with the upper pole fused to the lower pole of the left kidney along with moderate pelvicalyceal dilatation of the left kidney along with PCN in situ. (c) Nephrostogram shows adequate patency of left PCN tube with dilatation of the left pelvic calyceal system

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Figure 9 Case 9: An 8-year-old female child, known case of antenatally diagnosed bilateral hydronephrosis with right ureterocele, who underwent cystoscopy and deroofing of right ureterocele, complaints of intermittent right flank pain for 3 months. Urodynamic study revealed a normal normal-capacity bladder with normal urethral pressure with no urinary incontinence and no significant residual volume. (a) Ultrasonography of the patient shows bilateral hydronephrosis with right ureterocele with classical cobra head sign. (b) MCU of the patient shows an oval lucent defect at the right trigone with no vesicoureteric reflux along with smooth bladder outline and no diverticulum. The magnetic resonance urography, coronal (c) and axial (d) sections depicts large right ureterocele with bilateral hydronephrosis. (e) Renal dynamic scintigraphy of the patient reveals a small and hydronephrotic left kidney with severely impaired function (18%) and nonobstructive clearance with mild hydronephrosis of the right kidney with preserved function (82%) and nonobstructive clearance. There is visualization of the right mid to distal ureter due to ureterocele in the delayed static image. (f) Dimercaptosuccinic acid of the patient revealed a small and contracted impaired functioning left kidney with normal functioning right kidney with no focal cortical scars

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Figure 10 Case 10: A 16-year-old male child with a history of bladder exstrophy epispadias complex developed right Grade 5 vesicoureteric reflux (VUR). He underwent monsplasty and right Deflux procedure and passed urine in stream with a dry period of 1 h. The child developed repeated urinary tract infections for the last 4 years. (a) The patient was evaluated again to assess the bilateral VUR status. MCU of the patient depicted bilateral VUR with hydroureteronephrosis and diverticulated bladder. (b) Ultrasonography of the patient showed bilateral hydroureteronephrosis. (c) Dimercaptosuccinic acid was done to assess for evidence of bilateral renal scars due to bilateral VUR, and it showed preserved functioning bilateral kidneys with multiple focal cortical scars (left > right). Based on the overall anatomical and functional status, the child is planned for gastric neobladder

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Figure 11 Case 11: (a) Renal dynamic scintigraphy to assess the function of the transplanted kidneys in a 16-year-old boy with chronic kidney disease Grade 5 who underwent double renal transplant showed normal functioning bilateral kidneys with nonobstructive clearance

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Figure 12 Case 12: (a) Renal dynamic scintigraphy with (b) Single-photon emission computed tomography/computed tomography to localize ectopic left kidney and its functional status in a 16-year-old female patient with Ultrasonography suggestive of a small right kidney with severe cortical thinning and nonvisualization of the left kidney in the left renal fossa

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Conclusion

The diverse cases presented highlight the crucial role of various imaging modalities in diagnosing and managing a spectrum of surgical renal conditions in pediatric patients. The integration of different techniques, including USG, MRU, micturating cystourethrography (MCU), CT urography, RDS, and others, has been instrumental in providing comprehensive insights into the anatomical, functional, and pathological aspects of renal disorders in children.