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Wilms' tumor in the horseshoe kidney
Wilms' Tumor in The Horseshoe Kidney By V. L. Shashikumar, L. A. Somers, G. P. Pilling, IV, and S. t. Cresson
ORSESHOE K I D N E Y (fused ectopic kidney) has been reported in from 1 in 425 to 1 in 800 autopsies (performed at all ages)) In Campbell's 2 series of 51,800 autopsies (where 122 cases yielded the incidence of 1 to 425), the lesion occurred nearly twice as often in children, 1 to 312 (61 in 19,046 autopsies) as in adults, 1 to 538 (61 in 32, 834 autopsies), possibly indicating related early mortality. Probably because of its abnormal anatomy, the horseshoe kidney is particularly subject to hydronephrosis, infection, stone formation, and trauma. Somewhat less frequently, it is also Prone to neoplasia. A review of the world literature to December 1966 yielded 76 patients with cancer in a horseshoe kidney, including 14 with Wilms' tumor (Table 1). 3 Since then there have been three more reported cases of Wilms' tumor in a horseshoe kidney. 4 6 The purpose of our paper, which will describe three additional cases (in 48 cases of Wilms' tumor seen at St. Christopher's Hospital for Children from 1952 through 1972), is to emphasize the association of Wilms' tumor with horseshoe kidney and discuss specific diagnostic and therapeutic implications.
H
CASE REPORTS
Case 1 B. H., a 2-yr-old boy, had several previous admissions to St. Christopher's Hospital for Children. His medical problems included mental and motor retardation, palatal dysfunction with recurrent pneumonia, spastic quadriplegia, incontinenta pigmenti, and congenital heart disease. A paratesticular rhabdomyosarcoma had been treated by simple orchiectomy (no x-ray treatment or chemotherapy), and an intravenous pyelogram had demonstrated the presence of a horseshoe kidney. During his final hospitalization a lower abdominal mass was noted, and blood counts and bone marrow examination established the diagnosis of acute myelomonocytic leukemia. The patient died 2 days after admission. An autopsy revealed an unsuspected Wilms' tumor in the upper pole of the left component of the horseshoe kidney.
Case 2 T. B. was 2 yr old when she was admitted to another hospital for evaluation of a urinary tract infection. Physical examination revealed a lower midabdominal mass. An intravenous pyelogram showed a horseshoe kidney. During her hospitalization she developed hypertensive encephalop-
From St. Christopher's Hospital for Children, Philadelphia, Pa. V. L. Shashikumar, M.D., F.R.C.S. (C): Instructor in Pediatric Surgery, Temple University School of Medicine," Associate Attending Surgeon, St. Christopher's Hospital for Children, Philadelphia, Pa. Laurence A. Somers, M.D.: Associate Professor of Surgery, Temple University School of Medicine; and Attending Surgeon, St. Christopher's Hospital for Children, Philadelphia, Pa. George P. Pilling, IV, M.D.: Associate Professor of Surgery, Temple University School of Medicine; Attending Surgeon, St. Christopher's Hospital for Children, Philadelphia, Pa. Samuel L. Cresson, M.D.: Clinical Professor of Surgery; Chief of Division of Pediatric Surgery, Temple University School of Medicine; Director, Pediatric Surgery, St. Christopher's Hospital for Children, Philadelphia, Pa. Address requests for reprint. V. L. Shashikumar, M.D., 2600 N. Lawrence Street, Philadelphia, Pa. 19133. 9 1974 by Grune & Stratton, lnc. Journal of Pediatric Surgery, Vol 9, No. 2 (April), 1974
185
186
SHASHIKUMAR ET AL. Table 1. Wilms' Tumor in Horseshoe Kidney Year
Pt. Age
Hildenbrand Gibbon Eliason and Stevens Rose and Wattenberg Smith McGinn and Wickham
1895 1909 1944 1945 1946 1946
-4 yr 6 yr 21 mo lOmo 2 yr
-M F M M F
Campbell Firstar AFIP Lawlor et al. Beck and Helviko Sidaway Latham and Smith McQuiggan and Cerny Kraft 4 Bhatnagar, K. K.6 Montagnini et al. s St. Christopher's Hospital for Children St. Christopher's Hospital for Children St. Christopher's Hospital for Children
1951 1955 1957 1959 1960 1962 1962 1965 1968 1968 1969 1971 1971 t972
-15 mo 6yr 31/2 yr 5 yr 14 mo 2Yz yr 9 mo -9 mo 13 mo 23 mo 20 mo 4 yr
-F F F F M M F -M -M F M
No.
1 2 3 4 5 6
7 8 9 10 11 12 13 14 15 16 17 18 19 20
Author
Pt. Sex
Site of Tumor
Right kidney Left kidney Isthmus Left kidney Left kidney, isthmus, and lower pole of right kidney Left kidney Left kidney Right kidney and isthmus Isthmus Right kidney Right kidney Right kidney
Left kidney Left kidney Left kidney Right kidney Isthmus
athy and was transferred to St. Christopher's Hospital for Children. She had hypertension, polyurea, hyponatremia, hypochloremia, hypokalemia, alkalosis, and an elevated serum aldosterone. Renal angiograms confirmed the diagnosis of horseshoe kidney, but there was no evidence of a tumor. The left renal vein renin level was high, and the right renal vein renin was too high to be measured. At exploratory laparotomy a tumor was found arising from the hilum of the right half of the horseshoe kidney, and a right nephrectomy was carried out, including the isthmus. Microscopic examination revealed Wilms' tumor. Postoperatively, the hypertension subsided, blood chemistries reverted to normal, and polyurea disappeared. She received actinomycin D postoperatively (no x-ray treatment), and has had no recurrence in 19 mo.
Case 3 s. L., a 4-yr-old boy, was admitted to St. Christopher's Hospital for Children with acute abdominal pain. Laboratory studies at the time of admission showed a 3-g drop in hemoglobin from a determination done elsewhere 12 hr previously. X-ray films showed a soft-tissue mass in the midabdomen. At laparotomy, intraperitoneal bleeding from a mass in the root of the mesentery was encountered. The mass was partially removed and hemostasis achieved. A diagnosis of Wilms' tumor was made by microscopic examination. Postoperative intravenous pyelogram and an angiogram failed to demonstrate any abnormalities in the kidneys. At reexploration 2 days later, a tumor was found arising from the right half and isthmus of a horseshoe kidney and extending into the mesentery of the small bowel. A right nephrectomy, including the isthmus, was performed, and all of the grossly involved small bowel mesentery was removed en bloc. The operative procedure was complicated by accidental transection of the left ureter, which was primarily repaired. The postoperative course was complicated by hepatitis, evisceration, and acute renal failure, necessitating parenteral hyperalimentation and hemodialysis. The patient was discharged 43 days after admission, and thereafter received x-ray therapy (1800 rads to entire abdomen) as well as actinomycin D according to the National Wilms' Tumor Study Protocol. He has remained free of recurrence for 14 too.
WILMS' TUMOR
187
DISCUSSION Horseshoe kidney is the most c o m m o n variety of renal fusion. By definition, the two kidneys are fused together by a solid mass of tissue at either pole, giving the appearance of a horseshoe. Fusion occurs at the lower pole in 9 0 ~ of the cases. Horseshoe kidneys are situated at a lower level than normal kidneys, with the isthmus in front of the aorta and vena cava, generally at the level of the 4th or 5th lumbar vertebra, sometimes even lower in the pelvis. 7 (Gutierrez in an excellent review has depicted the various anatomical variations of horseshoe kidneys.) 7 Anomalies of the renal pelvis and ureter are common. The ureters usually pass in front of the isthmus, but may pass behind it, and may be duplicated on one or both sides. The blood vessels of horseshoe kidneys show wide variation in site of origin, number, and distribution, so that no two cases are quite alike. Generally there are four to six renal arteries running laterally and caudally, two to each hilum and one or two to the isthmus. The diagnosis of either horseshoe kidney or Wilms' tumor in a horseshoe kidney may not be easy. Reviewed literature indicates that the diagnosis of Wilms' tumor in a horseshoe kidney was frequently missed by x-ray studies, probably due to the rotation of the kidneys on their long axes. For example, the patient reported by Rose and Wattenberg 8 was operated upon ,because of a kidney stone, and the Wilms' tumor in the isthmus was an incidental finding. Periodic intravenous pyelograms have been suggested for patients with congenital aniridia and hemihypertrophy, in which the incidence of associated Wilms' tumor is known to be high, to diagnose the tumor at an early stage (Miller et al. have reviewed 440 cases of Wilms' tumor which included six patients with congenital aniridia, three with hemihypertrophy, and four with horseshoe kidneys). 9 Should the child with a horseshoe kidney be on a Wilms' tumor surveillance program? An argument against x-ray surveillance is the above-mentioned difficulty in diagnosis by intravenous pyelography and angiography. Because of its position in the midline overlying the spine, a horseshoe kidney (unlike the normally situated kidney), however, is readily accessible to physical examination. We suggest that, because of the predisposition of horseshoe kidney to develop Wilms' tumor, children with known horseshoe kidneys should undergo frequent periodic abdominal palpation to identify a Wilms' tumor at an early stage. In addition, since most horseshoe kidneys are identified after the onset of urinary tract symptoms, and since most of the symptomatic horseshoe kidneys require some kind of surgical treatment, the surgical plan should include a thorough examination of the entire horseshoe kidney. Two other features concerning diagnosis are noteworthy. Case 2 demonstrates the dramatic manifestation of renin-induced hypertension as a presenting problem; the result of surgical excision was equally dramatic. Other cases of renin-producing Wilms' tumors have been reported recently. ~~ In Case 3, intraperitoneal hemorrhage was a very unusual clinical manifestation of Wilms' tumor. In all cases reviewed in the literature, it was possible to carry out the surgical treatment at the time of the initial laparotomy. However, if at the time of laparotomy the lesion is too extensive for resection, a second laparotomy could
188
SHASHIKUMAR ET AL.
be carried out after a course of radiation treatment. A t u m o r arising from any part of the kidney requires resection of that half of the horseshoe kidney, including the isthmus. When the isthmus is represented by a simple fibrous bridge, resection of the kidney alone should suffice. The importance of resection of the isthmus along with one of the kidneys is emphasized by Culp and Winterringer H in their review of operations on 105 horseshoe kidneys. When functional isthmic tissue is left behind, a urinary fistula may result, if the isthmus originally drained through the pelvis of the resected kidney. When the tumor arises from the isthmus, isthmusectomy, including lower poles of both kidneys, should be carried out. As indicated earlier, horseshoe kidneys frequently have an anomalous blood supply complicating surgical removal. Also, because of the abnormal anatomy, the ureter of the normal side is particularly prone to operative injury as occurred in our third patient. Both of our surviving patients were treated according to the National Wilms' T u m o r Study Protocol, and received actinomycin D a n d / o r vincristine according to the protocol. The postoperative radiation therapy of Wilms' tumor in a horseshoe kidney must be modified. In Stages I and II, when x-ray treatment is directed to the t u m o r bed alone, dosage must be modified because the contralateral horseshoe c o m p o n e n t is so close to the midline that its shielding decreases the total a m o u n t of irradiation. (In Stage III, in which the entire abdomen is irradiated, the difference between radiation therapy of a normally situated kidney and a horseshoe kidney is not significant). Follow-up data on the cases reported in the literature are not available to determine the prognosis for Wilms' tumor arising in a horseshoe kidney. Both of our patients are surviving for 14 mo and 19 mo without recurrence. There are no reports in the literature of a second tumor developing subsequently in the remaining kidney. Only one of the reported patients had part of the other kidney involved at the time of the original operation, and it was included in the resection. SUMMARY
Three cases of Wilms' tumor arising in horseshoe kidneys are presented and added to the 17 reported cases in the world literature. The anatomy of the horseshoe kidney is reviewed. Diagnosis of a Wilms' tumor in a horseshoe kidney is difficult. It is suggested that the presence of a horseshoe kidney in a child warrants prophylactic surveillance by frequent periodic physical examination to ensure early diagnosis and treatment of a Wilms' t u m o r should it occur. The surgical treatment is resection of the involved side including the isthmus. Frequent anatomical variations complicate the surgical removal. There are not enough statistical data available in the literature to indicate the prognosis of a Wilms' t u m o r arising from a horseshoe kidney. REFERENCES
1. Lawlor JB, kattimer JK, Wolff JA: Wilms' tumor in a horse-shoe kidney. Arch Surg 81: 803, 1960 2. Campbell MF, Harrison JH (eds.): Urology, Vol 2. Philadelphia, Saunders, 1970
3. Blackard CE, Mellinger GT: Cancer in a horse-shoekidney, Arch Surg97:616, 1968 4. Krafft VL: Wilms' tumor in hufeisenniere. Zentralbl Chir 93:1583, 1968 5. Montagnini R, Manicia A, Crisci E, et al:
WILMS' TUMOR
Tumore di Wilms su rene a ferro di cavallo. AI Policlinico 76:305, 1969 6. Bhatnagar KK: Wilms' tumor in a horseshoe kidney. Indian J Surg 30:186, 1968 7. Gutierrez R: The clinical management of horse-shoe kidney. Am J Surg 14:657, 1931 8. Rose DK, Wattenberg CA: Wilms' tumor in the isthmus of a horse-shoe kidney, Urol Cutan Rev 49:365, 1945 9. Miller RW, Fraumeni JF Jr, Manning
18g
MD: Association of Wilms tumor with aniridia, hemihypertrophy and other congenital malformations. N Engl J Med 270:922, 1964 10. Mitchell JD, Baxter T J, Blair-West JR et al: Renin levels in nephroblastoma (Wilms' tumor), Arch Dis Child 45:376, 1970 11. Culp OS, Winterringer JR: Surgical treatment of horse-shoe kidney: Comparison of results after various types of operations. J Urol 73:747, 1955
ORSESHOE K I D N E Y (fused ectopic kidney) has been reported in from 1 in 425 to 1 in 800 autopsies (performed at all ages)) In Campbell's 2 series of 51,800 autopsies (where 122 cases yielded the incidence of 1 to 425), the lesion occurred nearly twice as often in children, 1 to 312 (61 in 19,046 autopsies) as in adults, 1 to 538 (61 in 32, 834 autopsies), possibly indicating related early mortality. Probably because of its abnormal anatomy, the horseshoe kidney is particularly subject to hydronephrosis, infection, stone formation, and trauma. Somewhat less frequently, it is also Prone to neoplasia. A review of the world literature to December 1966 yielded 76 patients with cancer in a horseshoe kidney, including 14 with Wilms' tumor (Table 1). 3 Since then there have been three more reported cases of Wilms' tumor in a horseshoe kidney. 4 6 The purpose of our paper, which will describe three additional cases (in 48 cases of Wilms' tumor seen at St. Christopher's Hospital for Children from 1952 through 1972), is to emphasize the association of Wilms' tumor with horseshoe kidney and discuss specific diagnostic and therapeutic implications.
H
CASE REPORTS
Case 1 B. H., a 2-yr-old boy, had several previous admissions to St. Christopher's Hospital for Children. His medical problems included mental and motor retardation, palatal dysfunction with recurrent pneumonia, spastic quadriplegia, incontinenta pigmenti, and congenital heart disease. A paratesticular rhabdomyosarcoma had been treated by simple orchiectomy (no x-ray treatment or chemotherapy), and an intravenous pyelogram had demonstrated the presence of a horseshoe kidney. During his final hospitalization a lower abdominal mass was noted, and blood counts and bone marrow examination established the diagnosis of acute myelomonocytic leukemia. The patient died 2 days after admission. An autopsy revealed an unsuspected Wilms' tumor in the upper pole of the left component of the horseshoe kidney.
Case 2 T. B. was 2 yr old when she was admitted to another hospital for evaluation of a urinary tract infection. Physical examination revealed a lower midabdominal mass. An intravenous pyelogram showed a horseshoe kidney. During her hospitalization she developed hypertensive encephalop-
From St. Christopher's Hospital for Children, Philadelphia, Pa. V. L. Shashikumar, M.D., F.R.C.S. (C): Instructor in Pediatric Surgery, Temple University School of Medicine," Associate Attending Surgeon, St. Christopher's Hospital for Children, Philadelphia, Pa. Laurence A. Somers, M.D.: Associate Professor of Surgery, Temple University School of Medicine; and Attending Surgeon, St. Christopher's Hospital for Children, Philadelphia, Pa. George P. Pilling, IV, M.D.: Associate Professor of Surgery, Temple University School of Medicine; Attending Surgeon, St. Christopher's Hospital for Children, Philadelphia, Pa. Samuel L. Cresson, M.D.: Clinical Professor of Surgery; Chief of Division of Pediatric Surgery, Temple University School of Medicine; Director, Pediatric Surgery, St. Christopher's Hospital for Children, Philadelphia, Pa. Address requests for reprint. V. L. Shashikumar, M.D., 2600 N. Lawrence Street, Philadelphia, Pa. 19133. 9 1974 by Grune & Stratton, lnc. Journal of Pediatric Surgery, Vol 9, No. 2 (April), 1974
185
186
SHASHIKUMAR ET AL. Table 1. Wilms' Tumor in Horseshoe Kidney Year
Pt. Age
Hildenbrand Gibbon Eliason and Stevens Rose and Wattenberg Smith McGinn and Wickham
1895 1909 1944 1945 1946 1946
-4 yr 6 yr 21 mo lOmo 2 yr
-M F M M F
Campbell Firstar AFIP Lawlor et al. Beck and Helviko Sidaway Latham and Smith McQuiggan and Cerny Kraft 4 Bhatnagar, K. K.6 Montagnini et al. s St. Christopher's Hospital for Children St. Christopher's Hospital for Children St. Christopher's Hospital for Children
1951 1955 1957 1959 1960 1962 1962 1965 1968 1968 1969 1971 1971 t972
-15 mo 6yr 31/2 yr 5 yr 14 mo 2Yz yr 9 mo -9 mo 13 mo 23 mo 20 mo 4 yr
-F F F F M M F -M -M F M
No.
1 2 3 4 5 6
7 8 9 10 11 12 13 14 15 16 17 18 19 20
Author
Pt. Sex
Site of Tumor
Right kidney Left kidney Isthmus Left kidney Left kidney, isthmus, and lower pole of right kidney Left kidney Left kidney Right kidney and isthmus Isthmus Right kidney Right kidney Right kidney
Left kidney Left kidney Left kidney Right kidney Isthmus
athy and was transferred to St. Christopher's Hospital for Children. She had hypertension, polyurea, hyponatremia, hypochloremia, hypokalemia, alkalosis, and an elevated serum aldosterone. Renal angiograms confirmed the diagnosis of horseshoe kidney, but there was no evidence of a tumor. The left renal vein renin level was high, and the right renal vein renin was too high to be measured. At exploratory laparotomy a tumor was found arising from the hilum of the right half of the horseshoe kidney, and a right nephrectomy was carried out, including the isthmus. Microscopic examination revealed Wilms' tumor. Postoperatively, the hypertension subsided, blood chemistries reverted to normal, and polyurea disappeared. She received actinomycin D postoperatively (no x-ray treatment), and has had no recurrence in 19 mo.
Case 3 s. L., a 4-yr-old boy, was admitted to St. Christopher's Hospital for Children with acute abdominal pain. Laboratory studies at the time of admission showed a 3-g drop in hemoglobin from a determination done elsewhere 12 hr previously. X-ray films showed a soft-tissue mass in the midabdomen. At laparotomy, intraperitoneal bleeding from a mass in the root of the mesentery was encountered. The mass was partially removed and hemostasis achieved. A diagnosis of Wilms' tumor was made by microscopic examination. Postoperative intravenous pyelogram and an angiogram failed to demonstrate any abnormalities in the kidneys. At reexploration 2 days later, a tumor was found arising from the right half and isthmus of a horseshoe kidney and extending into the mesentery of the small bowel. A right nephrectomy, including the isthmus, was performed, and all of the grossly involved small bowel mesentery was removed en bloc. The operative procedure was complicated by accidental transection of the left ureter, which was primarily repaired. The postoperative course was complicated by hepatitis, evisceration, and acute renal failure, necessitating parenteral hyperalimentation and hemodialysis. The patient was discharged 43 days after admission, and thereafter received x-ray therapy (1800 rads to entire abdomen) as well as actinomycin D according to the National Wilms' Tumor Study Protocol. He has remained free of recurrence for 14 too.
WILMS' TUMOR
187
DISCUSSION Horseshoe kidney is the most c o m m o n variety of renal fusion. By definition, the two kidneys are fused together by a solid mass of tissue at either pole, giving the appearance of a horseshoe. Fusion occurs at the lower pole in 9 0 ~ of the cases. Horseshoe kidneys are situated at a lower level than normal kidneys, with the isthmus in front of the aorta and vena cava, generally at the level of the 4th or 5th lumbar vertebra, sometimes even lower in the pelvis. 7 (Gutierrez in an excellent review has depicted the various anatomical variations of horseshoe kidneys.) 7 Anomalies of the renal pelvis and ureter are common. The ureters usually pass in front of the isthmus, but may pass behind it, and may be duplicated on one or both sides. The blood vessels of horseshoe kidneys show wide variation in site of origin, number, and distribution, so that no two cases are quite alike. Generally there are four to six renal arteries running laterally and caudally, two to each hilum and one or two to the isthmus. The diagnosis of either horseshoe kidney or Wilms' tumor in a horseshoe kidney may not be easy. Reviewed literature indicates that the diagnosis of Wilms' tumor in a horseshoe kidney was frequently missed by x-ray studies, probably due to the rotation of the kidneys on their long axes. For example, the patient reported by Rose and Wattenberg 8 was operated upon ,because of a kidney stone, and the Wilms' tumor in the isthmus was an incidental finding. Periodic intravenous pyelograms have been suggested for patients with congenital aniridia and hemihypertrophy, in which the incidence of associated Wilms' tumor is known to be high, to diagnose the tumor at an early stage (Miller et al. have reviewed 440 cases of Wilms' tumor which included six patients with congenital aniridia, three with hemihypertrophy, and four with horseshoe kidneys). 9 Should the child with a horseshoe kidney be on a Wilms' tumor surveillance program? An argument against x-ray surveillance is the above-mentioned difficulty in diagnosis by intravenous pyelography and angiography. Because of its position in the midline overlying the spine, a horseshoe kidney (unlike the normally situated kidney), however, is readily accessible to physical examination. We suggest that, because of the predisposition of horseshoe kidney to develop Wilms' tumor, children with known horseshoe kidneys should undergo frequent periodic abdominal palpation to identify a Wilms' tumor at an early stage. In addition, since most horseshoe kidneys are identified after the onset of urinary tract symptoms, and since most of the symptomatic horseshoe kidneys require some kind of surgical treatment, the surgical plan should include a thorough examination of the entire horseshoe kidney. Two other features concerning diagnosis are noteworthy. Case 2 demonstrates the dramatic manifestation of renin-induced hypertension as a presenting problem; the result of surgical excision was equally dramatic. Other cases of renin-producing Wilms' tumors have been reported recently. ~~ In Case 3, intraperitoneal hemorrhage was a very unusual clinical manifestation of Wilms' tumor. In all cases reviewed in the literature, it was possible to carry out the surgical treatment at the time of the initial laparotomy. However, if at the time of laparotomy the lesion is too extensive for resection, a second laparotomy could
188
SHASHIKUMAR ET AL.
be carried out after a course of radiation treatment. A t u m o r arising from any part of the kidney requires resection of that half of the horseshoe kidney, including the isthmus. When the isthmus is represented by a simple fibrous bridge, resection of the kidney alone should suffice. The importance of resection of the isthmus along with one of the kidneys is emphasized by Culp and Winterringer H in their review of operations on 105 horseshoe kidneys. When functional isthmic tissue is left behind, a urinary fistula may result, if the isthmus originally drained through the pelvis of the resected kidney. When the tumor arises from the isthmus, isthmusectomy, including lower poles of both kidneys, should be carried out. As indicated earlier, horseshoe kidneys frequently have an anomalous blood supply complicating surgical removal. Also, because of the abnormal anatomy, the ureter of the normal side is particularly prone to operative injury as occurred in our third patient. Both of our surviving patients were treated according to the National Wilms' T u m o r Study Protocol, and received actinomycin D a n d / o r vincristine according to the protocol. The postoperative radiation therapy of Wilms' tumor in a horseshoe kidney must be modified. In Stages I and II, when x-ray treatment is directed to the t u m o r bed alone, dosage must be modified because the contralateral horseshoe c o m p o n e n t is so close to the midline that its shielding decreases the total a m o u n t of irradiation. (In Stage III, in which the entire abdomen is irradiated, the difference between radiation therapy of a normally situated kidney and a horseshoe kidney is not significant). Follow-up data on the cases reported in the literature are not available to determine the prognosis for Wilms' tumor arising in a horseshoe kidney. Both of our patients are surviving for 14 mo and 19 mo without recurrence. There are no reports in the literature of a second tumor developing subsequently in the remaining kidney. Only one of the reported patients had part of the other kidney involved at the time of the original operation, and it was included in the resection. SUMMARY
Three cases of Wilms' tumor arising in horseshoe kidneys are presented and added to the 17 reported cases in the world literature. The anatomy of the horseshoe kidney is reviewed. Diagnosis of a Wilms' tumor in a horseshoe kidney is difficult. It is suggested that the presence of a horseshoe kidney in a child warrants prophylactic surveillance by frequent periodic physical examination to ensure early diagnosis and treatment of a Wilms' t u m o r should it occur. The surgical treatment is resection of the involved side including the isthmus. Frequent anatomical variations complicate the surgical removal. There are not enough statistical data available in the literature to indicate the prognosis of a Wilms' t u m o r arising from a horseshoe kidney. REFERENCES
1. Lawlor JB, kattimer JK, Wolff JA: Wilms' tumor in a horse-shoe kidney. Arch Surg 81: 803, 1960 2. Campbell MF, Harrison JH (eds.): Urology, Vol 2. Philadelphia, Saunders, 1970
3. Blackard CE, Mellinger GT: Cancer in a horse-shoekidney, Arch Surg97:616, 1968 4. Krafft VL: Wilms' tumor in hufeisenniere. Zentralbl Chir 93:1583, 1968 5. Montagnini R, Manicia A, Crisci E, et al:
WILMS' TUMOR
Tumore di Wilms su rene a ferro di cavallo. AI Policlinico 76:305, 1969 6. Bhatnagar KK: Wilms' tumor in a horseshoe kidney. Indian J Surg 30:186, 1968 7. Gutierrez R: The clinical management of horse-shoe kidney. Am J Surg 14:657, 1931 8. Rose DK, Wattenberg CA: Wilms' tumor in the isthmus of a horse-shoe kidney, Urol Cutan Rev 49:365, 1945 9. Miller RW, Fraumeni JF Jr, Manning
18g
MD: Association of Wilms tumor with aniridia, hemihypertrophy and other congenital malformations. N Engl J Med 270:922, 1964 10. Mitchell JD, Baxter T J, Blair-West JR et al: Renin levels in nephroblastoma (Wilms' tumor), Arch Dis Child 45:376, 1970 11. Culp OS, Winterringer JR: Surgical treatment of horse-shoe kidney: Comparison of results after various types of operations. J Urol 73:747, 1955