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Saudi Journal of Kidney Diseases and Transplantation
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Year : 2021  |  Volume : 32  |  Issue : 2  |  Page : 574-578
Polycystic horseshoe kidney case report: Genetically reviewed

1 Nephrology Unit; Department of Medicine, King Saud University Medical City, Riyadh, Saudi Arabia
2 Department of Medicine, King Saud University Medical City, Riyadh, Saudi Arabia
3 Department of Obstetrics and Gynecology, King Saud University Medical City, Riyadh, Saudi Arabia
4 Departmentof Medicine, King Saud University Medical City, Riyadh, Saudi Arabia

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Date of Web Publication11-Jan-2022


Autosomal dominant polycystic kidney disease (ADPKD) is the most common genetic renal disease, with a reported prevalence ranging from one in 400 to one in 1000. ADPKD accounts for as high as 10% of end-stage renal disease cases. It is characterized by cystic formation replacing kidney parenchyma leading to renal enlargement and renal functional impairment. Consequently, it is associated with renal and extrarenal complications contributing to high mortality. On the other hand, horseshoe kidney (HSK) is a common congenital renal anomaly, with an incidence ranging between one in 400 and 600. Surprisingly, the coexistence of both distinct common clinical conditions is extremely rare, and it is thought that the incidence of polycystic HSK varies from one in 134,000 to one in 8,000,000 cases. Although the particular genetic association is not established, familial cases raise the question of whether they are related. We report this case to cultivate the current medical literature regarding this rare entity.

How to cite this article:
Alobaili SS, Aljasser SM, Asseri AS, Alotaibi DA. Polycystic horseshoe kidney case report: Genetically reviewed. Saudi J Kidney Dis Transpl 2021;32:574-8

How to cite this URL:
Alobaili SS, Aljasser SM, Asseri AS, Alotaibi DA. Polycystic horseshoe kidney case report: Genetically reviewed. Saudi J Kidney Dis Transpl [serial online] 2021 [cited 2022 Sep 26];32:574-8. Available from: https://www.sjkdt.org/text.asp?2021/32/2/574/335474

   Introduction Top

Autosomal dominant polycystic kidney disease (ADPKD) is one of the most commonly inherited diseases.[1] In fact, it is the most common genetic renal disease, with a prevalence of one in 400–1000 live births.[2] It has been documented that ADPKD is responsible for 10% of end-stage kidney disease cases.[1] Moreover, it is reported to be responsible for about 6%–9% of kidney transplant recipients.[3] ADPKD is characterized by cystic formation within the kidney leading to renal enlargement and renal functional impairment.[4] It is recognized to have many extrarenal manifestations including but not limited to intra-cranial berry aneurism, hepatic cysts, valvular heart diseases, and colonic diverticular disease. Hence, high mortality rate particularly due to cardiovascular disease was observed.[5] The disease is genetically heterogeneous which results from mutant genes known as PKD1 which comprises approximately 85% of ADPKD cases followed by PKD2 which is responsible for the remaining 15% and finally PKD3 that is only found in certain unlinked families.[6] However, as in any genetic disease, de novo mutation may occur which would explain new cases with unremarkable family history.[7]

On the other hand, horseshoe kidney (HSK) is a common congenital renal anomaly, with an incidence ranging between one in 400 and 600 with male predominance as male: female ratio is 2:1.[8] HSK originates from abnormal renal ascendance and malrotation during embryogenesis that eventually causes the typical fusion of the two lower poles by the renal parenchyma or fibrous tissue and forming a horseshoe morphology.[8],[9] Although no recognized genetic determinant of HSK reported to date, it is still found to be reported in identical twins and siblings.[10]

Unexpectedly, the coexistence of both distinct common clinical conditions is extremely rare, and it is thought that the incidence of polycystic HSK varies from one in 134,000 to one in 8,000,000 cases.[11] We believe that with only a few cases reported in the literature, the association between ADPKD and HSK is still equivocal. Nevertheless, the observation of HSK and ADPKD in the same family indicates that they are related in one way or another. We report this case to cultivate the current medical literature regarding this rare entity.

   Case Report Top

A 47-year-old Saudi male was referred to a nephrology outpatient clinic in King Saud University Medical City (KSUMC) for hypertension secondary to polycystic kidney disease.

He has been initially seen in a urology clinic after a spontaneous passage of a kidney stone. He underwent sonographic assessment which revealed bilateral renal enlargement with innumerable cysts [Figure 1].
Figure 1: Ultrasonography image demonstrates bilateral renal enlargement with innumerable cysts replacing the renal parenchyma as well as tiny bilateral calcification. The remaining renal parenchyma demonstrates increase cortical echogenicity with no hydronephrosis. The right and the left kidneys were found to be approximately 16.3 cm ×7.6 cm and 14.4 cm ×8.1 cm, respectively.

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Computed tomography (CT) scanning provided that both kidneys were attached at the lower pole with multiple bilateral nonobstructing stones [Figure 2]. Both imaging findings were consistent with polycystic HSK.
Figure 2: Computerized tomography image illustrates horseshoe kidney with multiple bilateral innumerable cysts consistent with APKD. Some of them showed dense mural calcifications along with multiple bilateral nonobstructing kidney stones. Abdominal organs were grossly seen with no identified abnormality.

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Further evaluation revealed a history of multiple renal stone passages and repeated urinary infections. However, he currently does not complain of gross hematuria, flank pain, abdominal pain, fever, or lower urinary tract symptoms.

The patient denies any well-established diagnosis of APKD or chronic kidney disease (CKD) in the family. Clinically he has a blood pressure of 153/99 mm Hg, and he has a body mass index of 27.4.

A systemic physical examination revealed the presence of palpable kidneys. On investigation, he has hemoglobin of 15.9 g/dL, and the rest of complete blood count was within the normal limits, blood urea nitrogen: 8.4 mg/dL, creatinine: 130 μmol/L, and estimated glome-rular filtration rate: 55 mL/min/1.73 m2.

A 24-h urine collection was done in two different occasions, based on the adherence to low protein diet and low salt diet [Table 1].
Table 1: Twenty-four-hour urine collection.

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Gene sequencing for APK1 was as follows: heterozygous variant c.11315_11316insp. (Ala3773Profs*59), which genetically confirms the diagnosis of PKD type 1.

The patient was started on amlodipine for hypertension, along with education on lifestyle modification. Risk factors for progression of CKD were addressed and discussed in detail. Family screening for APKD was encouraged.

Informed consent was obtained from the patient for the publication of this case report.

   Discussion Top

This case emphasizes the clinical presentation and genetic mutation of polycystic HSK disease, which is a combination of two distinct renal disorders ADPKD and HSK.[12]

ADPKD is the most common hereditary renal disease[2] which results from mutations in the expression gene of the proteins polycystin-1 and polycystin-2 in ADPKD type 1 and ADPKD type 2, respectively.[12]

In ADPKD, the kidney is mainly formed by multiple cysts which are displacing the functioning renal tissue that not only causes large appearing kidneys but also leads to a continuous deterioration of the renal function due to the progressive cystic dilatation of the renal tubules.[1],[4] Therefore, it is found to be the third leading cause of end-stage kidney disease and responsible for 10% of the cases.[1],[13]

The vast majority of ADPKD patients present in the fourth decade of life. ADPKD is associated with high morbidity and mortality as it is considered to be a multisystem disease which may manifest as hepatic cysts, diverticular disease, cardiac valve abnormalities, and cerebral aneurysms.[1],[14]

ADPKD has an increased mortality rate that ranges between 1.6 and 2.88 folds, with cardiovascular events being the most common cause of mortality in those patients.[4]

On the other hand, HSK is probably the most common renal fusion anomaly,[13] with a reported incidence of one in 134,000–800,000 live births, and it is an asymptomatic condition which frequently found incidentally.[15] However, it is well established that it may increase the risk of nephrolithiasis, ureteropelvic junction syndrome, and renovascular hypertension.[16]

The clinical presentation of polycystic HSK disease varies widely in the current literature;[4] pyelonephritis,[14] sepsis,[17] gross hematuria,[18] loin pain,[19] vague abdominal pain,[13] abdominal mass,[18] infertility,[12] and ESKD for transplant[11],[20],[21],[22] were the reported presentations. In contrast, in our case, the patient presented with HTN and history of recurrent renal stones and infections.

ADPKD is associated with a heterogeneous mutation in three different genes: the PKD1 locus on chromosome 16p13, 3, which has been reported in 85% of the patients tested; PKD2 on chromosome 4q 13-23; and finally, PKD3;[1],[22] our patient mutation is a PKD1 [c.11315_11316insp. (Ala3773Profs*59)].

The systemic manifestations of the disease and its complications mentioned previously can be attributed to the fact that ADPKD genes are widely expressed through the body. Moreover, their proteins (polycystin-1 and polycystin-2) are associated with cyst formation.[16]

However, up to what we know, no genetic correlation has been found between PKD1 AND PKD2 genes and HSK disease.[12]

The diagnosis of ADPKD is usually reached by clinical examination, urography, and ultrasound or CT scan of the abdomen.[4] In our case, the patient was found to be hypertensive, with palpable kidneys on physical examination. Ultrasonography and CT studies are provided in [Figure 1] and [Figure 2].

In such cases, maintaining blood pressure is crucial since it is considered the most important modifiable cardiovascular risk factor in ADPKD patients. Thus, early and effective control of the blood pressure may prompt a significant rule in preserving kidney function and preventing cardiovascular events.[4],[5]

In that case, management of high blood pressure starts with lifestyle modifications such as salt restriction <2 g/day, limiting caffeine intake, smoking cessation, and adequate fluid intake (3 L/day).[5] Indeed, our patient is a nonsmoker and exercises regularly, yet a trial of lifestyle changes was not adequately effective. Accordingly, escalation of management was necessary by introducing antihypertensive medication.

By far, the current literature advises to start with ACEI and ARB for ADPKD with preserved kidney function. However, those with reduced kidney function might be better to be managed with other antihypertensive such as a beta-blocker or a calcium channel blocker.[5] In our case, the patient’s creatinine clearance was 16 mL/min and eGFR of 55 mL/min/1.73 m2 based on CKD-EPI formula, however he preferred to remain on CCB rather than taking an ACEI or ARB.

On review of the Update on Pathogenesis, Management, and Treatment of Hypertension in ADPKD study, it was recommended that keeping BP target of less than 130/80 mm Hg is optimal for ADKDP patients.[5]

We were successful to reach an average of BP (115/84 mm Hg) with 5 mg of amlodipine.

   Conclusion Top

Patients with polycystic HSK suffer from functional impairment. Together with structural abnormality making them prone to recurrent UTIs and nephrolithiasis, cautious follow-up along with prophylactic stone formation measures should be considered accordingly. It might also be a reasonable cause to screen them for hepatic cysts, berry aneurism, and valvular pathology. Keeping autosomal dominance mood of inheritance in mind, family members screening is crucial for early detection.

Conflict of interests: None declared.

   References Top

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Correspondence Address:
Saad S Alobaili
Nephrology Unit, Department of Medicine, King Saud University Medical City, Riyadh
Saudi Arabia
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/1319-2442.335474

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