and Spencer W. Beasley2
(1)
Department of Urology, Royal Children’s Hospital, Melbourne, Australia
(2)
Paediatric Surgery Department Otago, University Christchurch Hospital, Christchurch, New Zealand
Abstract
This chapter describes the assessment of undescended testis after a brief description of the normal embryology. Then there is a section on the acute scrotum and how to diagnose torsion of the testis or its appendages. Finally, there is a section on the groin lump, with a discussion of inguinal hernia.
Abnormalities of the male genitalia are extremely common and comprise a large part of general paediatric surgical practice. Accurate diagnosis of these disorders depends on a sound understanding of normal development, which provides the clinician with anatomical information as well as an appropriate list of differential diagnoses.
Embryology
In the human fetus, sexual differentiation begins at about 8 weeks of gestation, at which time the urogenital ridge contains the developing gonad, the regressing mesonephros (middle kidney) and the genital ducts. The Wolffian (mesonephric) duct develops into the vas deferens, epididymis and seminal vesicle under the stimulation of testosterone, while the Műllerian (paramesonephric) duct regresses under the action of a glycoprotein hormone, Mullerian-inhibiting substance (also known as anti-Műllerian hormone). The testis has descended to the internal inguinal ring by 14–17 weeks of gestation, where it remains quiescent until about 28 weeks (Fig. 4.1). Then there is rapid descent through the inguinal canal and into the scrotum, and by 35–40 weeks, descent is complete.
Fig. 4.1
The timing of testicular descent
During passage through the inguinal canal and migration across the pubic region and into the scrotum, the testis descends inside an outgrowth of peritoneum, the processus vaginalis, which invades the gubernacular mesenchyme (Fig. 4.2a). When descent is complete, the processus proximal to the testis obliterates (Fig. 4.2b). Failure of this obliteration is the cause of infantile herniae and hydroceles. Partial involution of the proximal processus without complete obliteration of the lumen results in an encysted hydrocele (Fig. 4.2c) or scrotal hydrocele (Fig. 4.2d). Total failure of involution at the level of the internal inguinal ring leads to a hernia (Fig. 4.2e, f). In the more common situation, only the proximal processus remains patent and the hernia presents as a lump at the external ring. Occasionally, the entire processus vaginalis remains widely patent, and the hernia presents clinically as a swelling extending from the external ring into the scrotum (‘inguinoscrotal’ or ‘complete’ hernia) (Fig. 4.2f). Involution of the processus begins as soon as the testis has descended; delay in this process of obliteration may result in a hernia because, after birth, increases in abdominal pressure (with crying, etc.) push the small bowel into the still patent processus and keep it open. A premature infant, therefore, is more likely to have incompletely descended testes and patent hernial sacs.
Fig 4.2
The mechanism of testicular descent through the inguinal canal (a), and obliteration of the processus vaginalis (b). Incomplete obliteration leads to an encysted hydrocele (c), a scrotal hydrocele (d), an incomplete hernia (e), or a complete hernia (inguinoscrotal hernia) (f)
The Undescended Testis
Testicular descent is a complex process initiated by hormones and executed by mechanical events; abnormalities of either of these may cause undescended testes. The hormonal signals are not known completely, but testosterone appears to be responsible for the second phase of descent through the inguinal canal into the scrotum. Testosterone acts at least in part via the genitofemoral nerve. Therefore, in children with undescended testes, one needs to consider androgen deficiency, even though it is much more common for maldescent to be caused by mechanical abnormalities or defects in the genitofemoral nerve.
Anatomical Landmarks for the Undescended Testis
The key to the clinical assessment of undescended testes is determination of their location. Undescended testes are arrested in the line of descent, or have deviated to an ‘ectopic’ or abnormal position. Rarely, the testis may remain inside the inguinal canal or abdomen, in which case it will be impalpable. A testis which has descended beyond the external inguinal ring but has not reached the scrotum will be deviated from the normal line of descent by the bony prominence of the pubic tubercle to lie lateral to the external ring (the commonest site for an ectopic testis). Here, it overlies the external oblique aponeurosis midway between the pubic tubercle and anterior superior iliac spine (Fig. 4.3). In this location, the testis remains within its tunica vaginalis under Scarpa’s fascia, and the ‘pouch’ this layer forms is sometimes referred to as the superficial inguinal pouch. If the testis cannot be palpated lateral to the external ring, there are three rare sites in which an ectopic testis may be located.
Fig. 4.3
The surface anatomy of the inguinal region and the arc along which the testis normally is located
They are (1) lateral to the scrotum in the thigh (femoral testis), (2) medial to the external ring (pubopenile testis) and (3) behind the scrotum (perineal testis).
It is vital to identify the position of the external ring and inguinal ligament to establish the anatomical location of the undescended testis (Fig. 4.4). The pubic tubercle marks the inferior margin of the external ring, and the inguinal ligament extends laterally from there to the anterior superior iliac spine. The skin crease most visible in the groin of small children does not correspond to the inguinal ligament, but rather the attachment of the superficial abdominal fascia (Scarpa’s fascia) to the fascia lata.
Fig. 4.4
The relationship of the bony landmarks and external rings to the skin creases
In small children, there is a tendency to underestimate how far above the scrotum is the superficial inguinal pouch, either leading to failure to locate a testis in the superficial inguinal pouch or to the misdiagnosis of an inguinal lymph node for a testis.
In the neonate, descended testes are easy to see, since the scrotum is flaccid and the skin very thin. Even at birth, the midpoint of the normal testis is at least 4–6 cm below the superior border of the pubis. In some premature children, the testes may not have completed descent by birth and may still be in the inguinal canal or pubic region. By 3 months, however, these ‘stragglers’ will be resident in the scrotum, allowing truly undescended testes to be distinguished from normally descended testes.
The Cremasteric Reflex
The spermatic cord contains the cremaster muscle, which modulates testicular temperature by retracting the testis from the scrotum. An active cremaster muscle causes a retractile testis, which may mimic an undescended testis when the testis is not found in the scrotum. The muscle is sensitive to circulating testosterone, with greater contractility of the muscle being observed when testosterone concentrations are low. When the testosterone concentration in the serum is high, contractility of the cremaster muscle is suppressed. During childhood, serum testosterone concentrations are high for the first few months after birth and at the onset of puberty (Fig. 4.5). Between the ages of about 2 and 8 years, serum testosterone concentrations are low, equivalent to those found in girls.
Fig. 4.5
The reciprocal relationship between the serum testosterone concentration and retractility of the testis
During this time, the contractility of the cremaster is enhanced markedly and leads to a high incidence of retractile testes in childhood. Since some children have a screening examination for undescended testes in the early primary school period when retractile testes are common, the distinction between true maldescent and retractile testes may be difficult.
Many children presenting later after the neonatal period with a non-scrotal testis have what we now recognize as acquired undescended testis. This is probably caused by failure of the processus vaginalis to completely obliterate, leaving a fibrous remnant in the spermatic cord which fails to elongate as the boy grows. This leads to the testis ‘ascending’ out of the scrotum by 4–8 years of age. These acquired undescended testes need to be distinguished from normally retractile testes.
There are certain criteria which should be met before a testis can be described as being retractile (Table 4.1). The testis should have been in the scrotum earlier in childhood, and there may be a history of it being visible low in the scrotum at birth.
Table 4.1
Criteria for the diagnosis of a retractile testis
1. Testis can be manipulated to the bottom of the scrotum |
2. Testis remains in the scrotum after manipulation |
3. Testis resides spontaneously in the scrotum some of the time |
4. Testis is normal is size |
The testis must reside there at some time during the day; usually, it is best seen at bath time when the warmth of the water suppresses cremasteric contraction and allows it to be fully descended. It should be possible to manipulate the testis to the bottom of the scrotum without undue tension on the cord. A testis that will only reach the top of the scrotum is maldescended. After manipulation of the testis to the bottom of the scrotum, the spermatic cord should not be so tight that the testis immediately springs back out. In other words, the retractile testis should remain in the scrotum spontaneously for a few seconds or minutes after manipulation. Where the testis is fully descended only when the spermatic cord is stretched tightly, maldescent must be assumed to be present. Finally, the testis should be normal in size, which implies that its development is not impaired by its position. This is a useful clinical point, since an undescended testis tends to become hypoplastic and smaller than a normal contralateral one.
History
Most boys with undescended testes present when someone notices that the scrotum appears to be empty. Knowledge of the location of the testes at birth is helpful. Where there were fully descended testes at birth, the empty scrotum of later childhood is likely to be caused by retractile testes or testes with acquired maldescent. This can be confirmed by asking about the position of the testes at times of relaxation of the cremaster, such as at bath time or after sleeping in a warm bed.
Physical Examination
Examination of the scrotum is aided when there is no stress or tension, and the room is warm: anxiety and cold stimulate the cremasteric reflex. The best way to avoid stress in a boy is to explain what is being done and to examine the genitalia gently. Inspection of the scrotum with the child standing will reveal whether it is large and contains testes or whether it is small and flat, suggesting the testes are not normally resident within it.
An alternative method is to get the small child to squat on the examining couch (Fig. 4.6a). This position causes automatic relaxation of the cremaster muscle and allows the testes to be seen in the scrotum. Older boys can be asked to sit on the couch, with the knees pulled up against the chest (Fig. 4.6b).
Fig. 4.6
Techniques to eliminate the effects of cremasteric contraction. Retractile testes appear in the scrotum when the small child squats (a) and the older boy sits in the knee-chest position (b)
Often, when a normal child lies supine, the testes can be seen within the scrotum. In obese boys, the scrotum may be difficult to see completely and, if there is cremasteric retraction, the testes may be lying near the upper part of the scrotum or higher where they are concealed by the skin because of the increased subcutaneous fat (Fig. 4.7a). Without touching the scrotum itself, the pubic skin can be retracted which often reveals the testes (Fig. 4.7b). It should be remembered that a testis is easy to see and feel only because of the extreme thinness of the skin of the scrotum. When the testis is in any other position, it is not only difficult to feel but also difficult to see (Fig. 4.8). If the scrotum is pulled up over the pubis to reveal the testis, it can then be palpated by the other hand and gently pulled caudally (Fig. 4.7c). Parental anxiety can be relieved by the clear demonstration of both testes in the scrotum (Fig. 4.7d).
Fig. 4.7
The technique of examining retractile testes. Initially the testes are often just out of the scrotum and hard to see (a). After traction on the pubic skin pulls the scrotum up, the testes become visible (b). The testes are snared by holding the spermatic cord and pulled down (c). It should then be possible to show the parents that both testes are in the scrotum (d)
Fig. 4.8
The relationship between the position of the testis and the overlying skin
Where the testis is truly undescended, the first step is to locate its position. The flat of the hand is placed gently over the inguinal region in the area of the superficial inguinal pouch (Fig. 4.9a). By gently rolling the fingertips round and round, the testis usually can be felt as a mobile, spherical structure between the subcutaneous fat and the abdominal wall muscles. The mobility of the testis in the superficial inguinal pouch is such that it is easily overlooked unless the flat of the hand is used. This prevents the testis slipping out unnoticed from under the examiner’s fingers.
Fig. 4.9
The technique of locating and delivering to the top of the scrotum an undescended or retractile testis. The mobile testis is located in the inguinal region (a). One hand then pushes the testis towards the scrotum (b), where the other hand attempts to snare it by holding the cord, to see how far down it will reach (c)
Once the testis is located, attempt to deliver it into the scrotum. Begin lateral to and above the known position of the testis, using the fingers of one hand to press firmly against the abdominal wall and attempt to ‘milk’ the testis towards the scrotum like a plough (Fig. 4.9b). If the testis can be manipulated to the pubis, it can then be snared through the thin scrotal skin by the opposite examining hand. The testis is held by compression of the spermatic cord, immediately proximal to the testis, rather than by holding the testis itself which would be painful to the child (Fig. 4.9c). By grasping the spermatic cord through the scrotal skin, the testis can be pulled down into the normal scrotal position and an estimate made of the degree of descent. This should be determined by the relationship of the testis to the scrotum (i.e. high, medium or low) and compared with the contralateral testis. An alternative procedure is to measure in centimetres the distance between the midpoint of the testis and the superior pubic crest. If the testis is descended normally, this should be at least 4–6 cm. A palpable testis is defined as being undescended if it is impossible to manipulate it into the scrotum to a distance of more than 4 cm below the pubic crest, or into the lower scrotum.
The Impalpable Testis
The testis may be completely impalpable, which suggests that it is either inside the inguinal canal or abdomen, or less commonly, absent. Although deep palpation over the inguinal canal may cause some discomfort, the intracanalicular testis is not palpable unless it can be ‘milked’ out through the external ring. Nevertheless, testes within the abdomen or the inguinal canal are rare, and in the majority of boys with undescended testes, a testis is palpable. The commonest reason for failure to feel a testis is failure to locate it in the superficial inguinal pouch probably because the clinician is misled by (1) the position of the skin creases, (2) the mobility of the testis or (3) a thick layer of subcutaneous fat which conceals the testis.
Two important clues should be sought if the testis cannot be found. First, the pubis adjacent to the external ring should be palpated carefully to feel for the emergent spermatic cord. An ectopic testis in a rare position may be traced by following the cord from the external ring (Fig. 4.10) to the testis. In addition, if the testis is canalicular, the external ring is open and can be felt as a V-shaped gap in the external oblique aponeurosis. Secondly, the size of the contralateral testis is helpful in assessing whether the testis is absent or impalpable because of its location within the inguinal canal or abdomen (Fig. 4.11). If one testis is absent (it may have undergone atrophy secondary to torsion during prenatal or perinatal descent), the contralateral organ undergoes compensatory hypertrophy, which may be apparent on clinical examination.
