Cryptorchidism refers to an absence of the testis in the scrotal sac. Testicular descent occurs in two stages: transabdominal and gubernacular. The descent of the testis can be arrested in its usual path of descent (true undescended testis) or can migrate from the usual path of descent (ectopic testis). Localising the missing testis is important for surgical planning, as well as for identification of complications that are more common with cryptorchidism. Ultrasound is the initial imaging modality to visualise, as well as localise the testis in cryptorchidism. However, ultrasound imaging is limited in visualising testes that are not superficial in location. This article highlights various examples of abnormal descent of the testis in usual as well as unusual locations and complications of undescended testes. Further evaluation with computed tomography scan or magnetic resonance imaging is needed in indeterminate cases and for identification of complications. We have highlighted the role of specific modalities with imaging findings in this pictorial review for the appropriate selection of each modality in clinical practice.
An absence of the testis in the scrotal sac is defined as cryptorchidism. The true undescended testis has arrested migration along its usual path of descent, or it is termed ectopic testis when it migrates from its usual path of descent to lie in an unusual location. An atrophic or congenital absence of the testis may simulate a similar situation. In infants, correct localisation of the testis is essential for surgical management, because the approach may vary with the location. In adults, however, it is still important to localise the testes and identify the complications.
Undescended testes are seen in approximately 1% – 6% of newborn males. The incidence is even higher in preterm infants, reported at 30%.
Around 70% of undescended testes are palpable on clinical examination. Clinically, it can sometimes be difficult to distinguish an undescended testis from a retractile testis, which is excessively mobile.
In 80% of patients with cryptorchidism, the testis is manually palpable in the inguinal canal.
Descent of the testes is along the normal path, but incomplete. The testis may be located in the inguinal canal (80%), near the pubic tubercle or, uncommonly, in the abdomen. The testis is often small and abnormal with a short spermatic cord.
Descent of the testes is away from the normal path. The testis is most often found in the superficial inguinal pouch. Other uncommon locations are perineal, abdominal wall, pelvic, crural, penile and femoral. The testis and spermatic cord are usually normal. Most frequent locations to aid a directed search for the testicles are shown in
The most frequent locations of true and ectopic undescended testis.
The purposes of imaging are to correctly localise the testis and assess viability and size (assess for atrophy). The aim is also to detect cases of vanished testis or agenesis. Ultrasound is an initial imaging modality to localise the testes, as well as to assess vascularity on colour Doppler imaging. If the testis is not identified in the scrotum on ultrasound, then the ‘tracking the cord’ technique is useful.
Greyscale ultrasound in a 6-month-old infant showing an undescended testis in the right inguinal canal (star).
Ultrasound is particularly useful in visualising superficially localised testes in the inguinal canal, inguinal pouch and subcutaneous location. Ultrasound has approximately 40%–50% sensitivity, 70%–80% specificity and around 88% accuracy for localisation of an undescended testis.
Sagittal ultrasound image of the left upper abdomen with a linear probe in a 2-year-old male child with left cryptorchidism.
Cross-sectional imaging modalities like computed tomography (CT) scans and magnetic resonance imaging (MRI) are used in indeterminate cases on ultrasonography, as well as in the assessment of complications. The testes appear hypodense on CT, and it may be difficult to differentiate them from lymph nodes or small cystic structures. CT scan involves significant radiation and raises concerns regarding the radiation dose as the majority of imaging for cryptorchidism occurs in the paediatric age group. CT scan is, however, superior in evaluating and staging known cases of testicular malignancy.
Magnetic resonance imaging has a higher sensitivity of approximately 90% and specificity of almost 100% in localising the testes compared to ultrasound.
(a) Coronal T2-weighted (T2W), (b) T2W axial and (c) T1-weighted (T1W) axial magnetic resonance images in a 12-month-old male with bilateral undescended testes, demonstrating ectopic testes at the superficial inguinal ring (white arrows).
(a) Coronal and (b) axial T2-weighted (T2W) magnetic resonance images in 9-month-old male child showing true undescended right testis (star) at the level of the root of penis, near the pubic tubercle (black arrow). The crura of the penis are seen at this level (circles). The inguinal canal (white arrow) is well visualised on coronal section.
Use of contrast-enhanced imaging in a 7-month-old male with an undescended left testis: (a) Coronal T2W image shows a true undescended testis in the left iliac fossa (bold white arrow). (b) Axial post-contrast subtraction image confirms a homogenously enhancing undescended left testis (bold arrow).
If until the age of 6 months (corrected for gestational age) a testis has not descended, surgery should be performed within the subsequent year, preferably by the age of 18 months. Histological examination proves that undescended testes suffer a progressive loss of germ cells as well as Leydig cells.
Seventy per cent of undescended testes are palpable manually, and in the remaining 30% of non-palpable undescended testis, the current algorithm is to perform abdominal-scrotal ultrasound first. Ultrasound is sensitive in visualising testes in the inguinoscrotal region or localised to the superficial abdomen wall and perineum. If the ultrasound findings are non-diagnostic, the next imaging modality is MRI. CT is non-invasive but is unreliable in identifying the testes and carries the risk of radiation. As per international guidelines from the American Association of Urology (2014), imaging in cryptorchidism is currently advocated as an adjunct. According to their guidelines, diagnostic laparoscopy or open exploration must be performed on all non-palpable cryptorchid patients.
Preoperative localisation of the testis definitely aids in surgical planning and approach.
Imaging algorithm in undescended testis.
Complications of undescended testes include an increased incidence of infertility, trauma, malignancy, torsion, other associated anomalies, as well as inguinal hernia. Although there has been dispute regarding orchiopexy reducing the risk of testicular cancer, it certainly increases the detection of malignancy through testicular self-examination.
Coronal non-contrast computed tomography abdomen of a 35-year-old male who presented to the emergency department with right flank pain.
A 30-year-old male patient with a left-sided undescended testis: (a) Ultrasound imaging in the left inguinal location showed an atrophic and echogenic testis (bold white arrowhead). Postoperative findings were consistent with testicular non-seminomatous germ cell tumour and epididymis disjunction. (b) Contrast computed tomography for systemic work-up revealed necrotic heterogeneous lymph nodal metastasis (bold white arrow) in the left para-aortic location, which regressed after chemotherapy.
If a testicle is located in the inguinal location, it might be prone to trauma or pressure against the pubic bone because of its superficial location (
A 15-year-old boy with trauma to the inguinal region presented to the emergency department.
A 30-year-old male presented to the emergency department with pain in the right inguinal region with a large inguinoscrotal hernia on clinical examination: (a) Coronal and (b) sagittal images of a computed tomography abdomen demonstrated an undescended testis (arrow on image a) along its path in the right lower abdomen, located lateral to the surface of urinary bladder (U). There was an associated large right omental hernia (arrow on image b). (c) The undescended testis is hyperintense (arrow on image c) on axial T2-weighted magnetic resonance images.
Clinicians and radiologists should be aware of the chronology of normal testicular descent, the common and uncommon locations of cryptorchidism, the specific imaging approach, as well as the complications associated with undescended testes.
The authors would like to thank Dr Devendra Kumar, Consultant, Hamad Medical Corporation, for his contribution of images.
The authors declare that they have no financial or personal relationships which may have inappropriately influenced them in writing this article.
P.N. was responsible for cases collection and writing of the manuscript. V.O. was responsible for editing of the manuscript and study design and D.K. contributed towards the images and case collection.