|Year : 2021 | Volume
| Issue : 2 | Page : 373-375
Horseshoe kidney with multiple bilateral renal calculi – Ultrasonography and intravenous urography evaluation
Asish Pavanan, Suresh Phatak, Bhavik Unadkat, Prerna Patwa
Department of Radio Diagnosis, Jawaharlal Nehru Medical College, Datta Meghe Institute of Medical Sciences (Deemed to be University), Wardha, Maharashtra, India
|Date of Submission||22-Oct-2020|
|Date of Decision||13-Jan-2021|
|Date of Acceptance||08-Apr-2021|
|Date of Web Publication||18-Oct-2021|
Dr. Suresh Phatak
Department of Radio-Diagnosis, Jawaharlal Nehru Medical College, Sawangi (Meghe), Wardha - 442 001, Maharashtra
Source of Support: None, Conflict of Interest: None
Horseshoe kidney is a congenital fusion anomaly of kidneys associated with many complications. A 57-year-old male presented with abdominal pain, hematuria, and burning micturition which on ultrasound examination was diagnosed to be a case of horseshoe kidney with multiple bilateral renal calculi. High-resolution sonography, radiography, and intravenous urography findings are discussed.
Keywords: High-resolution sonography, horseshoe kidney, renal fusion
|How to cite this article:|
Pavanan A, Phatak S, Unadkat B, Patwa P. Horseshoe kidney with multiple bilateral renal calculi – Ultrasonography and intravenous urography evaluation. J Datta Meghe Inst Med Sci Univ 2021;16:373-5
| Introduction|| |
Horseshoe kidney is characterized by two different functioning kidneys connected by an isthmus. The isthmus can be functional renal parenchyma or fibrous tissue. Horseshoe kidney is the most common renal fusion anomaly with an incidence of 1 in 500 in the normal population and has a well-described male preponderance (2:1). In identical twins and siblings, increased incidence has been reported.
The incidence of horseshoe kidney prenatally has not been well determined, so many horse shoe kidneys go undetected during fetal life.
Although abnormal location, orientation, and vascular supply of kidneys impairing urinary drainage are proposed to be the cause for renal stones in horseshoe kidney, the exact mechanism is still unclear.
| Case Report|| |
A 57-year-old male patient presented with abdominal pain, hematuria, and burning micturition. The pain was insidious in onset and was of high intensity more toward the right flank. The patient had three episodes of emesis since its onset. He did not report experiencing any chest pain, dyspnea, fever or bowel, and bladder dysfunction.
The patient underwent routine blood investigations along with renal and liver function tests which were normal at presentation. This was followed by radiography and ultrasonography (USG) of the abdomen and pelvis.
Abdominal radiograph showed vertical axis of both kidneys with bilateral calculi and scoliosis with convexity to right [Figure 1].
|Figure 1: Plain radiograph in a patient with a horseshoe kidney shows abnormal axis of the kidney with the lower poles being more medial than in the normal kidneys. Scoliosis and bilateral renal calculi can be visualized|
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In intravenous urography (IVU), kidneys lie vertically on either side of the midline and are joined at their lower poles by an opacified parenchymal isthmus suggestive of horseshoes kidney and showed multiple bilateral renal calculi and good contrast excretion bilaterally [Figure 2].
|Figure 2: IVU radiograph showing both kidneys rotated medially showing multiple calculi .There is good contrast excretion suggestive of normal functioning kidneys|
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USG revealed that kidneys are joined at lower pole having anterior orientation. During evaluation of the retroperitoneal space, isthmus was identified as solid structure anteriorly to the aorta connecting both kidneys [Figure 3]. The inferior border of the kidneys is not well defined due to bowel echoes. Three calculi measuring 18 mm, 13 mm, and 9 mm where found in the right kidney [Figure 4] and one calculus measuring 27 mm was found in the left kidney [Figure 5]. However, no hydronephrosis was seen. No free peritoneal fluid noted.
|Figure 3: Transabdominal ultrasound scanning horizontally along the midline shows isthmus joining the two lower poles of the kidney across the midline anterior to aorta|
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| Discussion|| |
During the 4th week of development, the ureteric bud which forms the collecting system and the metanephric blastema which forms the functioning kidney meets in the upper sacral region (S1–S2) through reciprocal induction. Aberration of this event leads to wide spectrum of renal anomalies.
Abnormal growth fluctuations and ventral flexion of the caudal fetus within a confined true pelvis cause fusion defects. During ascent, the metanephric blastema comes in close apposition as they pass through the arterial fork and fuse. The more complete the fusion, the more ectopic the position. Fusion anomalies can be either symmetrical or asymmetrical. Factors that influence both kidneys equally are presumed to cause symmetrical fusion anomalies. Differential displacement of renal masses results in asymmetrically shaped horseshoe kidneys.
Association of asymmetrical horseshoe kidneys with a number of vertebral conditions supports this hypothesis.
Ectopic mesenchymal tissue arising due to incomplete migration of nephrogenic cells across primitive streak has been suggested to be the cause of isthmus or bridge rather than “primary fusion.” This can explain incidence of certain tumors in horseshoe kidney.
The diagnosis of horseshoe kidney can be made on a plain radiograph as visible perinephric fat makes it easier to observe the renal outline. Altered renal axis is evident on plain radiograph showing lower poles more medial than expected. The kidney also may be situated lower than normal. On IVU, collecting system characteristically shows incomplete inward rotation of renal pelvis facing anteriorly along with inward deviated axis of lower poles because of the connection with isthmus.
On ultrasound, detection of midline isthmus connecting the lower poles of kidney across the midline is the key finding in making a diagnosis. This is best seen by placing the probe in the anterior abdominal wall and scanning horizontally along the midline in craniocaudal direction. Thin fibrotic band isthmus may be difficult to visualize. Features such as malrotation may be difficult to assess on USG. In children and thin adults, diagnosis is easy. However, in obese patients, it is difficult to observe the isthmus. Horseshoe kidney may be diagnosed in nuclear medicine using Technitium-labeled radionuclides. As functional renal tissue takes up these compounds, abnormal axis of a horseshoe kidney may be identified. It helps to identify whether isthmus is made up of functional renal tissue or fibrotic bands.
The investigation of choice for assessment of horseshoe kidney is contrast-enhanced computed tomography (CT) as it allows precise visualization of anatomy and relations of horseshoe kidney as well as evaluation of potential complications. Isthmus can be visualized crossing the midline and functional isthmus tissue enhances allowing to differentiate it from fibrous tissue. Magnetic resonance (MR) imaging also allows for accurate depiction of the anatomy and relations of horseshoe kidney and identifying complications. Vascular anatomy is identified more accurately in MR angiography. Due to embryological and anatomical background, horseshoe kidney is naturally predisposed to various disorders including pelvic ureteric obstruction, cystic dysplastic kidney, renal calculus disease, infections, reflux disease, tumors and trauma.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
| References|| |
Schiappacasse G, Aguirre J, Soffia P, Silva CS, Zilleruelo N. CT findings of the main pathological conditions associated with horseshoe kidneys. Br J Radiol 2015;88:20140456.
Cook WA, Stephens FD. Fused kidneys: Morphologic study and theory of embryogenesis. Birth Defects Orig Artic Ser 1977;13:327-40.
Fazio L, Razvi H, Chin JL. Malignancy in horseshoe kidneys: Review and discussion of surgical implications. Can J Urol 2003;10:1899-904.
Segura JW, Kelalis PP, Burke EC. Horseshoe kidney in children. J Urol 1972;108:333-6.
Banerjee B, Brett I. Ultrasound diagnosis of horseshoe kidney. Br J Radiol 1991;64:898-900.
O'Brien J, Buckley O, Doody O, Ward E, Persaud T, Torreggiani W. Imaging of horseshoe kidneys and their complications. J Med Imaging Radiat Oncol 2008;52:216-26.
Kao PF, Sheih CP, Tsui KH, Tsai MF, Tzen KY. The 99mTc-DMSA renal scan and 99mTc-DTPA diuretic renogram in children and adolescents with incidental diagnosis of horseshoe kidney. Nucl Med Commun 2003;24:525-30.
[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]