Undescended Testis
An undescended testis, or cryptorchidism, is a testis that has not moved into its normal position in the scrotum by the time it should have. It is the most common genital abnormality in newborn boys, affecting a small percentage of full-term infants and a considerably higher proportion of those born prematurely. Many descend on their own during the first few months of life, but those that have not done so by around six months are unlikely to, and surgical correction is recommended within the first year or so. Timing matters: the testis functions poorly outside the cooler environment of the scrotum, and early correction improves fertility outcomes, reduces—though does not eliminate—the risk of testicular cancer, and makes the testis examinable for life.
What is it?
The testes begin their development inside the abdomen, near the kidneys. During fetal life they migrate downward, passing through the inguinal canal and into the scrotum, with the final stage of this journey normally occurring in the last two months of pregnancy. This is why prematurity is so strongly associated with cryptorchidism: a boy born early may simply have been born before the descent finished.
The purpose of this migration is temperature. Sperm production requires a temperature roughly two to three degrees below core body temperature, and the scrotum provides it. A testis that remains inside the abdomen or high in the groin sits at body temperature, and over time the germ cells that produce sperm are progressively lost. Damage begins early—changes are detectable within the first year or two of life—which is the entire reason for correcting the position in infancy rather than waiting.
Cryptorchidism describes a testis that has not reached its normal scrotal position. Several distinct situations fall under and around this heading, and distinguishing them matters considerably.
A true undescended testis has stopped somewhere along its normal path of descent—within the abdomen, at the internal ring, within the inguinal canal, or just outside it but not reaching the scrotum. It cannot be brought fully down on examination, or if it can, it retracts immediately.
An ectopic testis has left the normal path entirely and lies in an abnormal location such as the perineum, the thigh, or the base of the penis. It is less common and requires surgical repositioning.
A retractile testis is not truly undescended and is important to recognise because it needs no surgery. An overactive cremasteric reflex pulls a normally descended testis up into the groin, particularly in cold conditions or when a child is anxious. The distinguishing feature is that a retractile testis can be brought down into the scrotum and stays there for a time before retracting. It is common in boys between roughly one and eleven years, generally resolves at puberty, and is managed with periodic review rather than surgery. However, a small proportion of retractile testes subsequently ascend and become genuinely undescended, so ongoing monitoring is appropriate rather than a single reassuring examination.
An ascending testis is one that was documented in the scrotum earlier but has subsequently risen out of it, typically discovered in mid-childhood. It requires surgical correction like a primary undescended testis.
An absent or vanishing testis occurs when the testis formed but was lost during development, most likely from torsion of its blood supply in fetal life. A small nubbin of remnant tissue is often found at exploration.
The causes are incompletely understood but involve the hormonal and mechanical processes governing descent. Descent depends on hormones including insulin-like peptide 3 and androgens acting on the structures that guide the testis downward, and disruption at any point can interrupt it. Prematurity and low birth weight are the strongest associations. Family history increases risk. Maternal smoking during pregnancy is associated, and there is ongoing research interest in whether environmental exposures affecting hormone signalling contribute to what appears to be a rising trend in some countries.
Cryptorchidism is also part of the concept of testicular dysgenesis syndrome, which groups undescended testis, hypospadias, impaired sperm production, and testicular cancer as related outcomes of disturbed testicular development. This framing helps explain why these conditions cluster together and why cancer risk is elevated even in the normally descended testis of a man with unilateral cryptorchidism.
The consequences of leaving a testis undescended are the reason the condition is treated rather than observed.
Fertility is affected, and the degree depends on whether one or both testes are involved. Men with a history of unilateral cryptorchidism have somewhat reduced sperm counts on average but generally normal fertility rates, close to those of unaffected men. Bilateral cryptorchidism carries a substantially greater impact, with a meaningful proportion of affected men experiencing significant impairment. Earlier surgery is associated with better outcomes, which is the main driver of current timing recommendations.
Testicular cancer risk is increased, and this is the association most parents ask about. The risk is several-fold higher than in the general population, though the absolute lifetime risk remains low. Two points refine this. First, orchidopexy reduces the risk but does not remove it, and correction at a younger age appears more protective. Second, the risk is also modestly increased in the normally descended contralateral testis, which indicates an underlying developmental abnormality rather than position alone being responsible. Bringing the testis into the scrotum also makes it examinable, so any tumour that does develop is likely to be found earlier.
Torsion is more likely in an undescended testis, and an inguinal hernia coexists in a high proportion of cases, since both relate to the same developmental process.
Psychological effects of an empty scrotum, particularly as boys become aware of body differences, are a genuine consideration and part of why correction is performed in early childhood.
Presentation is through examination rather than symptoms. The condition causes no pain or discomfort in a child. It is identified at newborn checks, at routine child health examinations, or by parents noticing an empty or asymmetric scrotum.
One presentation requires urgent rather than routine attention: bilateral non-palpable testes in a newborn. This can represent a disorder of sex development, and in particular congenital adrenal hyperplasia in a genetically female infant, which carries a risk of life-threatening salt-losing crisis. This situation warrants prompt specialist assessment including karyotype and hormonal evaluation rather than routine referral.
In older boys and adults, an uncorrected testis may present with groin pain from torsion, with an inguinal hernia, during infertility investigation, or—uncommonly but significantly—as a groin or abdominal mass that proves to be a tumour.
Diagnosis rests on examination, and one point about imaging deserves emphasis because it runs counter to intuition.
Careful examination by an experienced clinician, with the child warm and relaxed, in both lying and cross-legged positions, identifies whether a testis is palpable and whether it can be brought into the scrotum and held there. This distinguishes true cryptorchidism from a retractile testis, which is the most common diagnostic question and one that determines whether surgery is needed at all.
Imaging is not recommended for routine assessment of an undescended testis. This is a firm position in major guidelines and is worth explaining, since parents frequently expect a scan. Ultrasound cannot reliably identify an intra-abdominal testis and cannot exclude one, so a negative scan changes nothing—the child still requires laparoscopy if the testis is not palpable. MRI performs somewhat better but is expensive, often requires sedation in young children, and still does not achieve the accuracy needed to avoid surgical exploration. Ordering imaging therefore adds cost and delay without altering management, and delay in this condition has real consequences for the testis.
Laparoscopy is the definitive investigation for a non-palpable testis. It locates an intra-abdominal testis, identifies blind-ending vessels confirming absence, and allows the surgeon to proceed directly to the appropriate operation in the same session.
Hormonal testing and karyotype are indicated for bilateral non-palpable testes and when cryptorchidism coexists with hypospadias, since these combinations raise the possibility of a disorder of sex development.
Important to Know
The central principle is timing. Spontaneous descent is common in the first few months and uncommon after six months, so referral should occur promptly once it is clear the testis has not descended, with surgery ideally completed within the first eighteen months of life. Care is coordinated by paediatricians, paediatric surgeons, and paediatric urologists.
The rationale for early surgery is worth understanding, because it can otherwise seem like operating on a very young child for a problem causing no symptoms. Germ cell loss in an undescended testis begins early and is progressive, so each additional year of delay costs fertility potential. Earlier orchidopexy is also associated with lower subsequent cancer risk. And a testis in the scrotum can be examined throughout life, which matters given the elevated cancer risk.
Orchidopexy is the standard operation. For a palpable testis, it is typically a day-case procedure performed through a groin incision or, in selected cases, a scrotal approach, in which the testis is freed from its attachments, the associated hernia sac is dealt with, and the testis is placed and fixed in the scrotum. Success rates are high, particularly for testes that start lower down.
For a non-palpable testis, laparoscopy determines what is present. An intra-abdominal testis with adequate vessel length may be brought down in one operation. Where the vessels are too short, a staged procedure—dividing the testicular vessels at a first operation to allow collateral blood supply to develop, then bringing the testis down some months later—is used. Where vessels end blindly, the testis is absent and no further intervention is needed beyond removing any remnant.
Hormonal treatment with hCG or GnRH analogues is no longer recommended as primary therapy. Success rates are low, many apparent successes are retractile testes rather than genuinely undescended ones, and there are concerns about effects on the germ cells. Its use is now limited and specialised.
A retractile testis needs no surgery but does need follow-up, since a proportion later ascend. Annual examination through childhood is the usual approach, with surgery if the testis becomes genuinely undescended.
Management in adults who were never treated differs. Because such a testis contributes essentially nothing to fertility and carries an elevated cancer risk in a location that cannot be examined, removal is commonly recommended rather than repositioning, particularly beyond adolescence. The specific threshold and reasoning vary with age and individual circumstances and are discussed case by case. In older men, the balance shifts further toward removal or, in some situations, leaving it alone if surgical risk is high.
For parents, several practical points are worth knowing. Surgery is generally straightforward and performed as a day case, with recovery over days rather than weeks. Long-term function of the corrected testis is often good, though it may remain somewhat smaller than the other. One testis is sufficient for normal testosterone production and puberty, and usually for fertility. Follow-up after surgery checks position and growth.
Cancer risk deserves clear framing rather than either dismissal or alarm. The relative risk is elevated several-fold, but the absolute lifetime risk remains low—the great majority of men with a history of cryptorchidism never develop testicular cancer. What matters practically is that these men should be aware of the increased risk, know how their testes normally feel, and have any change assessed promptly. Cancer, if it develops, typically appears in young adulthood and is highly curable when found. This awareness is the single most useful long-term consequence to carry forward from a childhood diagnosis, and it is often not communicated to the man himself once he is old enough to act on it.
Fertility counselling is appropriate for men with a history of bilateral cryptorchidism, and semen analysis is reasonable when family planning begins, since impairment is more likely and options exist when it is identified early.
Care is coordinated by paediatric surgery or urology, with endocrinology and genetics involved for bilateral non-palpable testes or associated anomalies. Examination and operative findings drive management, with imaging playing a limited role.
Patient and parent education plays an important role. Understanding why surgery is recommended early despite the absence of symptoms, why a scan is not usually performed, that a retractile testis is different and does not need surgery, that one functioning testis is generally sufficient, and that lifelong awareness of the modest cancer risk is the main thing to carry into adulthood all contribute to appropriate care.
Red flag symptoms include bilateral non-palpable testes in a newborn, which requires urgent assessment for a disorder of sex development or congenital adrenal hyperplasia; a newborn or infant who is vomiting, feeding poorly, lethargic, or dehydrated in this context, which may indicate a salt-losing crisis and is an emergency; sudden severe groin or abdominal pain in a boy or man with an undescended testis, which suggests torsion and requires emergency assessment within hours; a firm or enlarging lump in the groin or abdomen; and in a man with a history of cryptorchidism, any new lump, firmness, or change in either testis. These warrant prompt or emergency evaluation depending on severity.