Reproduction in reptiles is very different to that of dog and cat patients, and the physiology and diagnosis of reproductive diseases in reptiles is complex. As well as the ability of some species to lay eggs, size and diet are primary factors which may influence sexual maturity in reptiles (Mader, 2006). Given that most reptiles are not sexually dimorphic, identifying the patient’s sex is fundamental but can be challenging in reptilian patients. In snakes, males will often have a longer tail; however, sexing can be confirmed through a technique known as “probing”, which involves inserting a metal probe into the cloaca and directing it towards the tail. In lizards, males will often have more evident femoral pores and hemipenile bulges at the base of the tail. In chelonians, males usually have a longer tail, the cloaca is more distal and the plastron is often concave. Species-specific sex variations may occur (Hedley, 2016).
The [reptilian] reproductive system is controlled by variables such as daylight hours, temperature, humidity, enclosure design and diet
The reproductive physiology of reptiles is extremely complex. The reproductive cycle is controlled by variables such as daylight hours, temperature, humidity, enclosure design and diet (Rivera, 2013). Reptiles can be oviparous (lizards, geckos, tortoises and snakes), viviparous (skinks) or ovoviviparous (boas and some chameleons) (Elliott, 2014). Parthenogenesis, or asexual reproduction, has also been reported in approximately 30 species of lizards (Mader, 2006).
Initial methods of examination
A thorough history is essential when assessing reptiles for reproductive disease. The source of the animals (captive versus wild), previous or current reproductive activity and husbandry information should be collected. It is critical to confirm whether the owner has provided a suitable laying site, as its absence is a common cause of dystocia. A physical examination should always be performed, as clinical signs can be quite non-specific, including an increase in basking time, lethargy, depression, anorexia, coelomic distention, cachexia, diarrhoea and change in posture (Mader, 2006).
Due to the variety of symptoms related to reproductive disease, it is recommended to perform a complete blood count and plasma biochemical analysis at the same time as the physical exam
Abdominal palpation is an easy diagnostic tool in snakes and lizards; however, radiology and ultrasonography are the most useful methods to identify the presence of follicles (Figure 1) or eggs. Radiology allows the identification of mineralised eggshells and can be helpful in chelonians (Gumpenberger, 2017) but is often not useful in snakes and lizards (Figure 2). Ultrasonography is preferred in lizards and snakes (Mader, 2006) as it is used to examine follicles, non-calcified eggs and the reproductive tract (Gumpenberger, 2017). Computed tomography can also be used with high levels of accuracy (Figure 3).
Due to the variety of symptoms related to reproductive disease, it is recommended to perform a complete blood count and plasma biochemical analysis at the same time as the physical exam. Hypercalcaemia may be indicative of reproductive activity in females due to the mobilisation of calcium during increased ovarian activity (Rivera, 2013).
Pre-ovulatory egg binding
Pre-ovulatory egg binding is also known as follicular stasis. This condition occurs when mature follicles fail to ovulate. The causes behind this reproductive disease can be varied, from incorrect husbandry to underlying disease (Hedley, 2016). Follicular stasis is most commonly seen in lizards. Clinical signs include anorexia, lethargy, weight loss, coelomic distention and collapse. Rupture of the follicle can occasionally cause secondary yolk coelomitis.
Diagnosis is usually confirmed via ultrasonography or radiography, where follicles can be visible as round soft tissue structures located in the middle of the coelom (Gumpenberger, 2017). Hyperalbuminaemia, hypercalcaemia and hyperphosphataemia, together with an explicative physical exam, are findings that may also lead to a correct diagnosis (Hedley, 2016). Supportive care is always necessary for these patients. Medical management can be attempted, but ovariectomy or ovariosalpingectomy is usually the preferred treatment (Mader, 2006). In extremely debilitated patients, euthanasia should be considered.
Post-ovulatory egg binding
Post-ovulatory egg binding is also known as dystocia. In this case, the patient encounters difficulty in giving birth or laying eggs. Dystocia can be classified as obstructive or non-obstructive. Obstructive dystocia is usually caused by abnormal eggs, narrow pelvis anatomy, oviduct torsion or neoplasia. Non-obstructive dystocia is usually related to poor husbandry, stress or underlying disease and is most common in primiparous females (Elliott, 2014). Dystocia is seen in all groups of reptiles, and symptoms involve lethargy, anorexia and sometimes restlessness and straining (Hedley, 2016).
On physical examination, it is occasionally possible to palpate eggs. Radiography is the preferred method of investigation for this reproductive disease and involves identifying soft tissue mineralised structures in the coelomic cavity (Gumpenberger, 2017). When assessing radiographs, it is vitally important to assess the quality of the eggs and their anatomical location (Hedley, 2016).
Dystocia is seen in all groups of reptiles. Symptoms involve lethargy, anorexia and sometimes restlessness and straining
Supportive care, such as fluid therapy and warmth, is always necessary. In tortoises, calcium gluconate and oxytocin (or vasotocin) can be administered to treat medically. However, surgery may be required. In snakes, eggs can sometimes be manipulated caudally and removed from the cloaca, but this comes with the risk of traumatising the reproductive tract. Ovocentesis is occasionally performed in snakes to attempt to reduce the size of the egg to allow the patient to pass it themselves. This technique carries the risk of causing iatrogenic egg peritonitis. Surgical removal remains the preferred form of treatment (Sykes, 2010; Hedley 2016; Gumpenberger, 2017).
Hypocalcaemiais encountered in sexually mature female reptiles with inadequate husbandry. The process of creating eggs uses a large amount of calcium as part of the eggshell. If female reptiles do not receive adequate calcium supplementation in their diet as required for the species, hypocalcaemic tetany of the oviduct can result in dystocia (Rivera, 2008). In addition, the patient may show other clinical signs of hypocalcaemia, including muscle fasciculations or tremors, paresis, tetany or seizures.
Cloacal prolapses can be caused by several different aetiologies, and the reproductive tract is often involved. Commonly prolapsed reproductive organs include the oviduct (Figure 4) and phallus or hemipenes. In cloacal prolapse cases, the prolapse must be treated as an emergency; however, the prolapse itself is a clinical sign of something underlying rather than a disease in itself. In most cases, an underlying aetiology causes the patient to strain excessively, resulting in a prolapse. Aetiologies can include but are not limited to dystocia (in females), infections, gastrointestinal parasitism, urolithiasis or excessive mating (in males) (McArthur and Machin, 2019).
Treatment for this reproductive disease includes analgesia, lubrication of the prolapsed tissue and manipulation to attempt to reduce the prolapse if the tissue is still viable. If the prolapse is not able to be manipulated, then surgery is the treatment of choice. Reptile phalluses only have a role in reproduction, so amputation is curative (Music and Strunk, 2016). Prolapse of the oviduct carries a poorer prognosis, and if the prolapse cannot be replaced, then a coeliotomy is required. If the tissue is devitalised or necrotic, it will need to be removed during the coeliotomy (McArthur and Machin, 2019). In all cases, identifying and treating the cause of the prolapse is essential to prevent further cloacal prolapses of other organs.
In cloacal prolapse cases, the prolapse must be treated as an emergency. However, the prolapse itself is a clinical sign of something underlying, rather than a disease in itself
Reptile reproductive diseases are commonly encountered in first opinion practice. As the presenting signs are often vague, some clinicians may not be aware that reproductive disease is present. However, reproductive disease should always be on a differential list when assessing an unwell reptile, especially when presented with a female or a patient of unknown sex. Most presentations of reproductive disease are not emergencies unless the patient is debilitated or a cloacal prolapse is present, in which case the patient must be assessed and treated as soon as possible.