bladder. The investigations that are ordered will depend on the taking of a medical history and an examination. The examination may involve a medical practitioner feeling in the suprapubic area for tenderness or fullness that might indicate an inflamed or full bladder. Blood tests may be ordered that may indicate inflammation; for example a full blood count may demonstrate elevated white blood cells, or a C-reactive protein may be elevated in an infection. Some forms of medical imaging exist to visualise the bladder. A bladder ultrasound may be conducted to view how much urine is within the bladder, indicating urinary retention. A urinary tract ultrasound, conducted by a more trained operator, may be conducted to view whether there are stones, tumours or sites of obstruction within the bladder and urinary tract. A CT scan may also be ordered. A flexible internal camera, called a cystoscope, can be inserted to view the internal appearance of the bladder and take a biopsy if required. Urodynamic testing can help to explain the symptoms. Other animals Mammals All mammals have a urinary bladder. This structure begins as an embryonic cloaca. In the vast majority, this eventually becomes differentiated into a dorsal part connected to the intestine and a ventral part which becomes associated with the urinogenital passage and urinary bladder. The only mammals in which this does not take place are the platypus and the spiny anteater both of which retain the cloaca into adulthood. The mammalian bladder is an organ that regularly stores a hyperosmotic concentration of urine. It therefore is relatively impermeable and has multiple epithelial layers. The urinary bladder of the cetaceans (whales and dolphins) is proportionally smaller than that of land-dwelling mammals. Reptiles In all reptiles, the urinogenital ducts and the anus both empty into an organ called a cloaca. In some reptiles, a midventral wall in the cloaca may open into a urinary bladder, but not all. It is present in all turtles and tortoises as well as most lizards but is lacking in the monitor lizard, the legless lizards. It is absent in the snakes, alligators, and crocodiles. Many turtles, tortoises, and lizards have proportionally very large bladders. Charles Darwin noted that the Galapagos tortoise had a bladder which could store up to 20% of its body weight. Such adaptations are the result of environments such as remote islands and deserts where water is very scarce. Other desert-dwelling