Physical Examination
Dysmorphism
Renal and Urinary Tract Anomalies Associated with Multiple Congenital Anomalies
Any dysmorphic feature (e.g., abnormal ears) should lead the clinician to look for other anomalies and structural defects. Appendix I-1 lists the major signs of multiple congenital anomalies associated with renal and urinary tract anomalies (see Chapters 38 and 43). The most typical sequence related to kidney disease is the oligohydramnios sequence, i.e., Potter syndrome, which may result from prolonged leakage of amniotic fluid or from intrauterine oligoanuria. Fetal deformation caused by severe oligohydramnios includes Potter facies, which is characterized by a redundant, wrinkled skin, flat nose, low-set ears, bilateral skin folds arising at the inner canthus, receding chin, and malposition of the hands and feet (368). Lung hypoplasia results from fetal compression as a result of the oligohydramnios (369) and, in some cases, massive abdominal distention. Even a short duration (1 week) of oligohydramnios can induce hypoplasia of the lung during the pseudoglandular period (12 to 16 weeks of GA) and the canalicular period (17 to 28 weeks of GA) (368,369,370 and 371).
Associations of Renal and Urinary Tract Anomalies with Single Signs
Upper urinary tract anomalies may be associated with several isolated anomalies (e.g., abnormal vertebrae, anorectal malformations) (see Appendix G-3); however, some of these associations are controversial (372,373 and 374). Ultrasonographic screening of infants with isolated single umbilical artery (UA) showed urinary tract malformations in 8/112 (7%) (373). A meta-analysis of studies using a more extensive urologic workup found a higher incidence (33/204, or 16.2 %); however, additional anomalies detected by this more extensive investigation were only minor (375). The presence of specific index signs should raise the suspicion of a known multiple congenital anomaly; the presence of vertebral or anorectal anomalies can suggest a possible VATER syndrome. Urinary tract abnormalities were detected in 6 infants with isolated preauricular tags (6/70; 8.6%) (376). Some signs may be an indication for performance of US only in some families (e.g., preauricular pits) (374). The risk of finding renal or urinary tract anomalies increases with the number of additional system anomalies and, in the case of hypospadias, with its severity (372).
Thus, it appears justified to obtain a US in newborn infants with specific types of single anomalies and in those with recognized multiple congenital anomalies.
Vital Signs and General Examination
Shock and asphyxia can lead to prerenal or intrinsic renal failure. Tachycardia, peripheral vasoconstriction, hypotension, or narrowing of the pulse pressure suggests hypovolemia or low-output cardiac failure, which places the infant at risk for prerenal failure. Tachyarrhythmia, premature ventricular contractions, or abnormal QRS complexes on cardiac monitoring may be the first sign of hyperkalemia, which may be as a result of, or related to, renal immaturity or renal failure. Seizures or coma may be as a result of hypertension or complications of renal failure.
Measurement and Evolution of Blood Pressure in the Neonatal Period
Accurate blood pressure measurement is obviously crucial not only to the evaluation of hypertension (see below), but also to the ongoing assessment of any neonate. Many neonates will have their blood pressure measured directly through an indwelling umbilical or radial artery catheter; this technique provides the most accurate method of measuring blood pressure, minor artifacts (such as from air bubbles or blood clots in the tubing) notwithstanding (377). Indwelling catheters also are helpful in the management of infants with hypertension as they make it possible to obtain frequent blood pressure determinations. This is discussed in more detail below.
The most commonly used indirect method of blood pressure measurement is the oscillometric technique, which directly measures mean arterial pressure (MAP) based on the oscillations of the arterial wall; systolic and diastolic blood pressure are then back-calculated from the MAP using manufacturer-specific algorithms. These devices are usually sufficiently accurate for routine clinical use, although it is important to note that the readings obtained by oscillometric devices may differ between 1 to 5 mm Hg compared to directly measured blood pressure (378). Shock may also lead to inaccurate oscillometric measurements (379). Despite these issues oscillometric devices clearly are useful for measuring blood pressure in infants without indwelling arterial catheters, and in infants that have been discharged from the nursery.
Selection of a proper sized cuff is also crucial for correct indirect blood pressure measurement. As discussed in the Fourth Report of the National High Blood Pressure Education Program (380), the length of the cuff bladder should be 80% to 100% of the arm circumference and the length of the cuff bladder should be 80% to 100% of the arm circumference. Leg blood pressures tend to be higher than those obtained in the arm (381,382,383,384); therefore it is important to have the nursing staff document in which extremity an infant’s blood pressure is being measured so that trends can be accurately followed over time.
Many studies have examined the pattern of normal blood pressure in normal and premature infants (384,385,386). Most recently, Zubrow and colleagues examined blood pressures obtained in over 600 infants of varying birth weights (BWs) and GAs admitted to 14 neonatal intensive care units (NICUs) (387). They found that blood pressure at birth is closely correlated with GA and BW (Appendix G1a&b). There is then a predictable increase in blood pressure over the first 5 days of life that is independent of these factors. Thereafter, blood pressure continues to rise gradually, with the most important determining factor being post conceptual age (Appendix G1c). These data provide a clinically useful method of determining whether an infant’s blood pressure is normal or elevated (388) (see Hypertension).
Blood pressure increases with the awake state, in the knee-chest position, with crying, pain, and during physical examination and procedures, or even during feeding (382,389,390 and 391). In some infants, blood pressure follows a circadian pattern (392). Tracking of blood pressure begins during the first months of life (393).
Chest
A small chest suggests hypoplastic lungs, which can be associated with renal and urinary tract malformations. Previous data suggesting an association of kidney and urinary tract malformations with polythelia, i.e., supernumerary nipples were not confirmed by a large study on 200 asymptomatic infants (394). Prerenal failure may result from CHF, PDA, and severe respiratory distress.
Abdomen
The physical examination of a newborn infant should include bimanual palpation of the abdomen for the presence of a normal kidney in each flank (212,213,225). The examination is easiest in the delivery room, before the bowel is filled with gas; later on, it is facilitated by relaxation of the abdominal wall musculature obtained, for instance, by eliciting the sucking reflex. Several characteristics of the kidneys should be evaluated, including location (normally in the flank; an ectopic kidney may be located in the pelvis), size (the normal size for a 3.3 ± 0.5 [mean ± SD] kg infant is 4.2 to 4.3 ± 0.5 cm) (395), and long axis (normally cephalocaudal). A horseshoe kidney may be suspected if the lower pole is closer to the midline than the upper pole. The consistency of a normal kidney is firm, in contrast to a cystic or a hydronephrotic kidney, which may be depressible. The surface normally is smooth, but large cysts can be palpated in multicystic or autosomal dominant polycystic kidneys.
Two thirds of abdominal masses are genito-urinary in origin and may be as a result of a polycystic/multicystic kidney, renal vein thrombosis, congenital or acquired hydronephrosis (e.g., as a result of a fungus ball or papillary necrosis), or a renal tumor (396,397). A suprapubic mass suggests bladder distention, which may result from lower urinary tract obstruction or an occult spinal cord lesion. In some patients, one or both kidneys cannot be palpated. This may be as a result of a less than optimal examination (e.g., absence of patient relaxation, bowel distention), unilateral renal agenesis, renal malposition (in which case the kidney may be felt at another place in the abdomen), or renal hypoplasia or aplasia. Some abnormalities of the abdominal wall, such as bladder exstrophy, cloacal exstrophy, and prune-belly syndrome, are associated with renal anomalies. Sphincter dysfunction may suggest an occult spinal dysraphism.
The umbilical cord should be checked for the presence of a single umbilical artery. Ano-rectal anomalies or am-biguous genitalia, including severe hypospadias (372), should raise the suspicion of associated renal or urologic malformations. Percussion of the abdomen may disclose ascites or a large bladder. In the absence of hydrops fetalis,
neonatal ascites commonly is as a result of the rupture of an obstructed urinary tract (398).
neonatal ascites commonly is as a result of the rupture of an obstructed urinary tract (398).
Limbs
Motor and sensory dysfunction of the lower limbs suggests an occult spinal dysraphism. Several limb anomalies are part of syndromes or sequences associated with renal or urinary tract malformations, such as skeletal dysplasia, caudal regression syndrome, radial aplasia, femoral hypoplasia, rocker bottom feet, compression deformation, polydactyly, syndactyly, and hemihypertrophy.
Hydration
Serial measurements of net body weight should be compared to the normal evolution of postnatal weight (399). Signs of dehydration include weight loss, dry skin and mucosae, sunken fontanelle, and signs of hypovolemia. In newborn infants, generalized edema usually starts around the eyes, at the perineum, and on the lateral sides of the trunk. Edema may be a sign of renal failure or nephrotic syndrome, among other causes.
Clinical Observations
Time of the First Postnatal Voiding
With early feeding, 97% of all infants void within 24 hours after birth (including in the delivery room) (400). Urine produced in utero normally is dilute, with an average osmolality less than 200 mOsm/kg. Higher osmolality in utero may result from obstructive urinary tract disease, poor tubular reabsorption of sodium, administration of oxytocin or indomethacin to the mother, or intrauterine asphyxia. In contrast, urine produced after birth usually is isotonic or hypertonic, probably as a result of increased release of oxytocin and ADH.
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