Congenital hydronephrosis: Correlation of fetal ultrasonographic findings with infant outcome Jane E. Corteville, MD, Diana L. Gray, MD, and James P. Crane, MD St. Louis, Missouri
Although congenital hydronephrosis is a common fetal disorder, ultrasonographic criteria for prenatal diagnosis remain poorly defined. In this study prenatal ultrasonographic findings were correlated with postnatal outcome in 63 fetuses with suspected hydronephrosis. Prenatal ultrasonographic measurements included length, anteroposterior diameter, and transverse diameter of the kidney and renal pelvis, as well as dorsal renal parenchymal thickness. In 45 of the 63 fetuses, hydronephrosis was confirmed postnatally. These infants were divided into two groups on the basis of renal status: (1) abnormal renal function and/or surgery required (n = 31) and (2) normal renal function with no surgery required (n = 14). The anteroposterior diameter of the renal pelvis was the simplest and most sensitive technique for prenatal diagnosis of congenital hydronephrosis, allowing identification of 100% of cases. Postnatal follow-up studies are warranted if an anteroposterior pelvic diameter is ~4 mm before 33 weeks or ~ 7 mm after 33 weeks. (AM J OSSTET GVNECOL 1991 ;165:384-8.)
Key words: Congenital hydronephrosis, prenatal diagnosis, ultrasonography, infant outcome Congenital hydronephrosis is a commonly encountered birth defect, occurring with a frequency of 1 in every 330 infants (unpublished data). Clinical presentation is variable and may include a palpable abdominal mass, intermittent pain, vomiting, failure to thrive, or urinary tract infection. Surgical correction of congenital hydronephrosis within 6 to 12 months of birth is typically associated with good outcome whereas delayed diagnosis carries an increased risk of renal impairment. I, 2 Unfortunately, diagnosis on clinical grounds alone is often delayed with 0.28, >0.30, >0.40, and >0.50 were analyzed (Table IV). An anteroposterior pelvis/kidney ratio of >0.28 was required to achieve a sensitivity of 90% to 100%. Transverse diameter of renal pelvis/kidney ratio. Thresholds of >0.3, >0.4, and >0.5 were selected for analysis (Table V). The threshold of >0.3 proved most sensitive, identifying 96% to 100% of fetuses with postnatally confirmed cong-enital hydroneDhrosis.
Congenital hydronephrosis-Ultrasonographic diagnosis
Volume 165 Number 2
387
Table V. Transverse diameter of pelvis/kidney versus risk of postnatal congenital hydronephrosis 14-23 wk Transverse diameter, pelvis / kidney ratio
Sensitivity
>0.30 >0.40 >0.50
96 72 52
(%)
I
24-32 wk
False-positive rate (%)
Sensitivity
51 51
100 86 60
41
I
(%)
33-42 wk
False-positive rate (%)
Sensitivity
37
100 88 77
35 31
(%)
1
False-positive rate (%)
26
27
23
Table VI. Kidney circumference / abdominal circumference versus risk of postnatal congenital hydronephrosis 14-23 wk
Kidney circumference / abdominal circumference ratio
Sensitivity
>0.28 >0.30 >0.32
90
24-32 wk
False-positive rate (%)
Sensitivity
95
49
89
76
43
58
(%)
I
44
Kidney / abdominal circumference ratio. Thresholds of>0.28, >0.30, and >0.32 were examined (Table VI). A threshold of >0.28 appeared optimal although sensitivity decreased to only 59% in late pregnancy. Renal parenchymal thickness. Although ultrasonographically measured parenchymal thickness might potentially reflect cortical atrophy, no threshold that accurately predicted infant outcome could be identified. Calicectasis. Dilated calyces were noted prenatally in only 47% (28/60) of hydronephrotic kidneys. While not highly sensitive for prenatal diagnosis of postnatally confirmed congenital hydronephrosis, calicectasis did correlate with morbidity. As noted in Table VII, surgery and renal compromise were significantly more common in fetuses with dilated calyces than in fetuses without calicectasis.
Comment Ultrasonographic recognition of a prominent fluid collection within the fetal renal pelvis represents a diagnostic dilemma. False-positive diagnosis of fetal hydronephrosis may lead to unwarranted parental anxiety, as well as unnecessary and expensive diagnostic studies after delivery. At the same time failure to recognize and promptly treat clinically significant obstructions may result in impaired renal function. Several ultrasonographic criteria have been proposed for prenatal diagnosis of congenital hydronephrosis; however, this is the first investigation to compare these parameters in the same population and correlate their accuracy in predicting infant outcome. Anteroposterior renal pelvic diameter is perhaps the most commonly used technique for diagnosing congenital hydronephrosis. Both Arger et al. 4 and Grignon et al. 5 considered an anteroposterior diameter ~ 10 mm to be predictive of abnormal outcome. In addition, Ar-
(%)
1
33-42 wk
False-positive rate (%)
Sensitivity
33
59
27
41
32
76
(%)
48
1
False-positive rate (%)
26 22
o
Table VII. Impact of calicectasis on postnatal outcome
Kidneys (No.) Surgery required (%)
Renal compromise (%)
Surgery with or without compromise (%)
Normal calyces
Dilated calyces
32
28
28
50
56
89
41
79
ger et al. i suggested follow-up scans in any fetus with an anteroposterior diameter of 25 mm. Data from the current investigation indicate that a threshold of 10 mm is too high. For example, 68% of fetuses with postnatally confirmed congenital hydronephrosis would be missed before 24 weeks' gestation (Table III). In contrast, a threshold of 4 mm yields a sensitivity of 100%. While the false-positive rate is higher with a 4 mm threshold, the goal is to identify all "at risk" fetuses. In addition, the false-positive rate declines as gestational age advances, falling to only 24% near term. After 33 weeks' gestation, a threshold of 7 mm can be used while still maintaining 100% sensitivity. The second analyzed ultrasonographic parameter was the ratio of the anteroposterior diameters of the renal pelvis and kidney. Both Arger et al. i and Kleiner et al. 6 suggested that a ratio exceeding 0.50 should be used for prenatal diagnosis of congenital hydronephrosis. Before 24 weeks' gestation, this threshold would fail to detect 60% of postnatally confirmed lesions; after 24 weeks, nearly 50% of affected fetuses would remain undetected (Table IV). To achieve a sensitivity of 90% to 100%, an anteroposterior pelvis/kid-
388
Corteville, Gray, and Crane
August 1991 Am J Obstet Gynecol
Table VIII. Anteroposterior pelvic diameter: Thresholds for counseling 14-23 wk
Anteroposterior pelvic diameter (mm) 10
CH (%)
o
41 53 82
I
24-32 wk
SIC
CH
(%)
(%)
o
o
19 40 73
I
33-42 wk
SIC
CH
(%)
(%)
o
o
6
67 82
38
13
86
72
33
o
I
SIC (%)
o
o
50 59
CH, Congenital hydronephrosis confirmed postnatally; SIC, postnatal surgery andlor evidence of renal compromise.
ney ratio of 0.28 is recommended. While this ratio is associated with a high false-positive rate in early pregnancy, progressive decline in the rate of false-positive results is noted as gestation advances. The third examined biometric approach to prenatal diagnosis of congenital hydronephrosis was the ratio of the transverse diameters of the renal pelvis versus the kidney. Jeanty and Romer0 7 described this technique in 1984 and considered a ratio 2:0.5 to be abnormal. In our study population this threshold identified only 52% of confirmed lesions before 24 weeks' gestation and missed 23% to 40% of affected fetuses during later pregnancy (Table V). A transverse pelvis/kidney ratio of 0.30 appeared more ideal, identifying nearly 100% of cases at all gestational ages. As with previously cited techniques, the false-positive rate declines with advancing gestational age. The kidney circumference/abdominal circumference ratio was originally described by Grannum et aJ.8 Although this method was developed as a means of quantifying renal enlargement in cystic kidney disease, an increased ratio also might be anticipated in congenital hydronephrosis. On examination of our data, a kidney circumference/abdominal circumference ratio of 0.28 appeared optimal during the midtrimester although sensitivity decreased to only 59% during late pregnancy (Table VI). Of all analyzed techniques for prenatal diagnosis of congenital hydronephrosis, the anteroposterior diameter of the renal pelvis is simplest and has sensitivity and false-positive rates that are equal or superior to those of other ultrasonographic approaches. Follow-up studies are warranted in 3 to 4 weeks if an anteroposterior pelvic diameter is 2:4 mm before 33 weeks or 2:7 mm after 33 weeks. Postnatal follow-up studies are recommended if persistent renal pelvic dilatation is evident. Neonatal ultrasonographic evaluation should be postponed for several days after delivery to assure that the infant is well hydrated and the full extent of any potential obstruction appreciated. If abnormal, additional diagnostic studies including intravenous pyelography and renal scintigraphy may be helpful in further
defining the lesion, as well as in delineating appropriate medical management. Table VIII provides useful information for counseling parents when a diagnosis of congenital hydronephrosis is suspected. For example, before 24 weeks' gestation, there is a 41 % chance of postnatally confirmed congenital hydronephrosis if the anteroposterior pelvic diameter is between 4 and 6 mm and a 19% risk for impaired renal function and/or surgery. The risk for adverse outcome increases to 40% if the anteroposterior diameter is between 7 and 9 mm and approaches 73% if 2:10 mm. It is clear from this study that congenital hydronephrosis is a clinically significant birth defect. Overall, 69% (31/45) of affected infants had related morbidity as defined by abnormal renal function and/or the need for surgical intervention. We hope this investigation clarifies appropriate ultrasonographic criteria for diagnosis of congenital hydronephrosis and provides useful guidelines for counseling and management of this common congenital malformation. REFERENCES 1. Mayor G, Genton N, Torrado A, GuignardJP. Renal func-
2. 3. 4. 5. 6. 7. 8.
tion in obstructive nephropathy: long-term effect of reconstructive surgery. Pediatrics 1975;56:740-7. Mathieu H, Loirat C, Macher MA, et al. Long-term outcome of children with malformative uropathies. lnt] Pediatr Nephrol 1985;6:3-12. Snyder HM, Lebowitz RL, Colodny AH, Bauer SB, Retik AB. Ureteropelvic junction obstruction in children. Urol Clin North Am 1980;7:273-89. Arger PH, Coleman BG, Mintz MC, et al. Routine fetal genitourinary tract screening. Radiology 1985; 156:485-9. Grignon A, Filion R, Filiatrault D, et al. Urinary tract dilatation in utero: classification and clinical applications. Radiology 1986;160:645-7. Kleiner B, Callen PW, Filly RA. Sonographic analysis of the fetus with ureteropelvic junction obstruction. AJR 1987;148:359-62. Jeanty P, Romero R. Are the kidneys normal? In: Brehm J], Boynton S, eds. Obstetrical ultrasound. New York: McGraw-Hill,1984:143-9. Grannum P, Bracken M, Silverman R, Hobbins ]C. Assessment of fetal kidney size in normal gestation by comparison of ratio of kidney circumference to abdominal circumference. AM] OBSTET GYNECOL 1980;136:249-54.
Although congenital hydronephrosis is a common fetal disorder, ultrasonographic criteria for prenatal diagnosis remain poorly defined. In this study prenatal ultrasonographic findings were correlated with postnatal outcome in 63 fetuses with suspected hydronephrosis. Prenatal ultrasonographic measurements included length, anteroposterior diameter, and transverse diameter of the kidney and renal pelvis, as well as dorsal renal parenchymal thickness. In 45 of the 63 fetuses, hydronephrosis was confirmed postnatally. These infants were divided into two groups on the basis of renal status: (1) abnormal renal function and/or surgery required (n = 31) and (2) normal renal function with no surgery required (n = 14). The anteroposterior diameter of the renal pelvis was the simplest and most sensitive technique for prenatal diagnosis of congenital hydronephrosis, allowing identification of 100% of cases. Postnatal follow-up studies are warranted if an anteroposterior pelvic diameter is ~4 mm before 33 weeks or ~ 7 mm after 33 weeks. (AM J OSSTET GVNECOL 1991 ;165:384-8.)
Key words: Congenital hydronephrosis, prenatal diagnosis, ultrasonography, infant outcome Congenital hydronephrosis is a commonly encountered birth defect, occurring with a frequency of 1 in every 330 infants (unpublished data). Clinical presentation is variable and may include a palpable abdominal mass, intermittent pain, vomiting, failure to thrive, or urinary tract infection. Surgical correction of congenital hydronephrosis within 6 to 12 months of birth is typically associated with good outcome whereas delayed diagnosis carries an increased risk of renal impairment. I, 2 Unfortunately, diagnosis on clinical grounds alone is often delayed with 0.28, >0.30, >0.40, and >0.50 were analyzed (Table IV). An anteroposterior pelvis/kidney ratio of >0.28 was required to achieve a sensitivity of 90% to 100%. Transverse diameter of renal pelvis/kidney ratio. Thresholds of >0.3, >0.4, and >0.5 were selected for analysis (Table V). The threshold of >0.3 proved most sensitive, identifying 96% to 100% of fetuses with postnatally confirmed cong-enital hydroneDhrosis.
Congenital hydronephrosis-Ultrasonographic diagnosis
Volume 165 Number 2
387
Table V. Transverse diameter of pelvis/kidney versus risk of postnatal congenital hydronephrosis 14-23 wk Transverse diameter, pelvis / kidney ratio
Sensitivity
>0.30 >0.40 >0.50
96 72 52
(%)
I
24-32 wk
False-positive rate (%)
Sensitivity
51 51
100 86 60
41
I
(%)
33-42 wk
False-positive rate (%)
Sensitivity
37
100 88 77
35 31
(%)
1
False-positive rate (%)
26
27
23
Table VI. Kidney circumference / abdominal circumference versus risk of postnatal congenital hydronephrosis 14-23 wk
Kidney circumference / abdominal circumference ratio
Sensitivity
>0.28 >0.30 >0.32
90
24-32 wk
False-positive rate (%)
Sensitivity
95
49
89
76
43
58
(%)
I
44
Kidney / abdominal circumference ratio. Thresholds of>0.28, >0.30, and >0.32 were examined (Table VI). A threshold of >0.28 appeared optimal although sensitivity decreased to only 59% in late pregnancy. Renal parenchymal thickness. Although ultrasonographically measured parenchymal thickness might potentially reflect cortical atrophy, no threshold that accurately predicted infant outcome could be identified. Calicectasis. Dilated calyces were noted prenatally in only 47% (28/60) of hydronephrotic kidneys. While not highly sensitive for prenatal diagnosis of postnatally confirmed congenital hydronephrosis, calicectasis did correlate with morbidity. As noted in Table VII, surgery and renal compromise were significantly more common in fetuses with dilated calyces than in fetuses without calicectasis.
Comment Ultrasonographic recognition of a prominent fluid collection within the fetal renal pelvis represents a diagnostic dilemma. False-positive diagnosis of fetal hydronephrosis may lead to unwarranted parental anxiety, as well as unnecessary and expensive diagnostic studies after delivery. At the same time failure to recognize and promptly treat clinically significant obstructions may result in impaired renal function. Several ultrasonographic criteria have been proposed for prenatal diagnosis of congenital hydronephrosis; however, this is the first investigation to compare these parameters in the same population and correlate their accuracy in predicting infant outcome. Anteroposterior renal pelvic diameter is perhaps the most commonly used technique for diagnosing congenital hydronephrosis. Both Arger et al. 4 and Grignon et al. 5 considered an anteroposterior diameter ~ 10 mm to be predictive of abnormal outcome. In addition, Ar-
(%)
1
33-42 wk
False-positive rate (%)
Sensitivity
33
59
27
41
32
76
(%)
48
1
False-positive rate (%)
26 22
o
Table VII. Impact of calicectasis on postnatal outcome
Kidneys (No.) Surgery required (%)
Renal compromise (%)
Surgery with or without compromise (%)
Normal calyces
Dilated calyces
32
28
28
50
56
89
41
79
ger et al. i suggested follow-up scans in any fetus with an anteroposterior diameter of 25 mm. Data from the current investigation indicate that a threshold of 10 mm is too high. For example, 68% of fetuses with postnatally confirmed congenital hydronephrosis would be missed before 24 weeks' gestation (Table III). In contrast, a threshold of 4 mm yields a sensitivity of 100%. While the false-positive rate is higher with a 4 mm threshold, the goal is to identify all "at risk" fetuses. In addition, the false-positive rate declines as gestational age advances, falling to only 24% near term. After 33 weeks' gestation, a threshold of 7 mm can be used while still maintaining 100% sensitivity. The second analyzed ultrasonographic parameter was the ratio of the anteroposterior diameters of the renal pelvis and kidney. Both Arger et al. i and Kleiner et al. 6 suggested that a ratio exceeding 0.50 should be used for prenatal diagnosis of congenital hydronephrosis. Before 24 weeks' gestation, this threshold would fail to detect 60% of postnatally confirmed lesions; after 24 weeks, nearly 50% of affected fetuses would remain undetected (Table IV). To achieve a sensitivity of 90% to 100%, an anteroposterior pelvis/kid-
388
Corteville, Gray, and Crane
August 1991 Am J Obstet Gynecol
Table VIII. Anteroposterior pelvic diameter: Thresholds for counseling 14-23 wk
Anteroposterior pelvic diameter (mm) 10
CH (%)
o
41 53 82
I
24-32 wk
SIC
CH
(%)
(%)
o
o
19 40 73
I
33-42 wk
SIC
CH
(%)
(%)
o
o
6
67 82
38
13
86
72
33
o
I
SIC (%)
o
o
50 59
CH, Congenital hydronephrosis confirmed postnatally; SIC, postnatal surgery andlor evidence of renal compromise.
ney ratio of 0.28 is recommended. While this ratio is associated with a high false-positive rate in early pregnancy, progressive decline in the rate of false-positive results is noted as gestation advances. The third examined biometric approach to prenatal diagnosis of congenital hydronephrosis was the ratio of the transverse diameters of the renal pelvis versus the kidney. Jeanty and Romer0 7 described this technique in 1984 and considered a ratio 2:0.5 to be abnormal. In our study population this threshold identified only 52% of confirmed lesions before 24 weeks' gestation and missed 23% to 40% of affected fetuses during later pregnancy (Table V). A transverse pelvis/kidney ratio of 0.30 appeared more ideal, identifying nearly 100% of cases at all gestational ages. As with previously cited techniques, the false-positive rate declines with advancing gestational age. The kidney circumference/abdominal circumference ratio was originally described by Grannum et aJ.8 Although this method was developed as a means of quantifying renal enlargement in cystic kidney disease, an increased ratio also might be anticipated in congenital hydronephrosis. On examination of our data, a kidney circumference/abdominal circumference ratio of 0.28 appeared optimal during the midtrimester although sensitivity decreased to only 59% during late pregnancy (Table VI). Of all analyzed techniques for prenatal diagnosis of congenital hydronephrosis, the anteroposterior diameter of the renal pelvis is simplest and has sensitivity and false-positive rates that are equal or superior to those of other ultrasonographic approaches. Follow-up studies are warranted in 3 to 4 weeks if an anteroposterior pelvic diameter is 2:4 mm before 33 weeks or 2:7 mm after 33 weeks. Postnatal follow-up studies are recommended if persistent renal pelvic dilatation is evident. Neonatal ultrasonographic evaluation should be postponed for several days after delivery to assure that the infant is well hydrated and the full extent of any potential obstruction appreciated. If abnormal, additional diagnostic studies including intravenous pyelography and renal scintigraphy may be helpful in further
defining the lesion, as well as in delineating appropriate medical management. Table VIII provides useful information for counseling parents when a diagnosis of congenital hydronephrosis is suspected. For example, before 24 weeks' gestation, there is a 41 % chance of postnatally confirmed congenital hydronephrosis if the anteroposterior pelvic diameter is between 4 and 6 mm and a 19% risk for impaired renal function and/or surgery. The risk for adverse outcome increases to 40% if the anteroposterior diameter is between 7 and 9 mm and approaches 73% if 2:10 mm. It is clear from this study that congenital hydronephrosis is a clinically significant birth defect. Overall, 69% (31/45) of affected infants had related morbidity as defined by abnormal renal function and/or the need for surgical intervention. We hope this investigation clarifies appropriate ultrasonographic criteria for diagnosis of congenital hydronephrosis and provides useful guidelines for counseling and management of this common congenital malformation. REFERENCES 1. Mayor G, Genton N, Torrado A, GuignardJP. Renal func-
2. 3. 4. 5. 6. 7. 8.
tion in obstructive nephropathy: long-term effect of reconstructive surgery. Pediatrics 1975;56:740-7. Mathieu H, Loirat C, Macher MA, et al. Long-term outcome of children with malformative uropathies. lnt] Pediatr Nephrol 1985;6:3-12. Snyder HM, Lebowitz RL, Colodny AH, Bauer SB, Retik AB. Ureteropelvic junction obstruction in children. Urol Clin North Am 1980;7:273-89. Arger PH, Coleman BG, Mintz MC, et al. Routine fetal genitourinary tract screening. Radiology 1985; 156:485-9. Grignon A, Filion R, Filiatrault D, et al. Urinary tract dilatation in utero: classification and clinical applications. Radiology 1986;160:645-7. Kleiner B, Callen PW, Filly RA. Sonographic analysis of the fetus with ureteropelvic junction obstruction. AJR 1987;148:359-62. Jeanty P, Romero R. Are the kidneys normal? In: Brehm J], Boynton S, eds. Obstetrical ultrasound. New York: McGraw-Hill,1984:143-9. Grannum P, Bracken M, Silverman R, Hobbins ]C. Assessment of fetal kidney size in normal gestation by comparison of ratio of kidney circumference to abdominal circumference. AM] OBSTET GYNECOL 1980;136:249-54.
