Abdomen and Pelvis 
progresses as the descending colon. 
The descending colon (Figs. 5-45, 5-46) is 
about 120 to 180 mm long and about 3 mm in di- 
ameter; it also has a grayish-green serous surface. 
It extends caudally along the left lateral abdominal 
wall; in male hamsters, it runs dorsal to the epi- 
didymal fatty tissue in a caudomedial direction and 
crosses the left ureter. In female hamsters, it crosses 
ventrally over the uterine horns. At about the level 
of the sacrum, the descending colon reaches the 
midline and, dorsal to the urinary bladder and the 
body of the uterus, runs between these organs and 
the sacrum where it continues into the rectum. 
5.6.3 Retroperitoneal Viscera and 
Relations 
5.6.3.1 Rectum 
In European hamsters the rectum of the male is 
considerably longer (40 to 60 mm) than that of the 
female (35 to 45 mm). It extends from the descend- 
ing colon through the pelvic cavity to the anus, 
which lies more caudally in males than in females. 
The grayish-green rectum lies dorsal to the uri- 
nary bladder, vagina and body of the uterus and 
ventral to the proximal caudal vertebrae and sac- 
rum in females. It runs dorsal to the bladder, ac- 
cessory glands and the origin of the penis, and ven- 
tral to the sacral and caudal vertebrae in males 
(Fig. 5-46). 
5.6.3.2 Urinary Organs 
The urinary organs {organa uropoetica) include 
the kidneys (ren), which secrete the urine; the ure- 
ters {ureter), which convey the urine to the bladder; 
the urinary bladder {vesica urinaria), which tem- 
porarily stores the urine and the urethra, through 
which the urine is discharged from the urinary 
bladder (Fig. 5-47). 
5.6.3.2.1 Kidney 
The kidneys constantly filter waste materials 
from the blood. They regulate body fluids and salts 
and maintain normal osmotic pressure of the blood 
and tissues. The bilaterally paired kidneys weigh 
about 930 mg each (Tables 2, 5) and lie retroperi- 
toneally in the lumbar region (Fig. 5-48). The 
axes of the kidneys lie oblique to the midsagittal 
plane of the body; the distance between the caudal 
poles {extremitates caudales) of the kidneys being 
18mm, while that between the cranial poles (e.>r- 
tremitates craniales) is only 11 mm. The right kid- 
ney lies between the first and the third lumbar ver- 
tebrae and is covered cranioventrally by the caudate 
lobe of the liver (Fig. 5-33). The hilus {hilus ren- 
alis) of the right kidney lies at the level of the trans- 
verse process of the third lumbar vertebra, while the 
hilus of the left kidney is situated between the third 
and fourth lumbar vertebrae. One renal artery {a. 
renalis) and one renal vein {v. renalis) pass over the 
hilus of each kidney (Figs. 5-33, 5-47). At the cra- 
nial end of each kidney lies an adrenal gland {gl. 
suprarenalis), which is separated from the kidney 
proper by fatty and connective tissue. 
The vessels to the right kidney originate more 
cranially than those supplying the left kidney (Fig. 
5-33). Craniodorsal to the left renal vein, the left 
renal artery originates from the abdominal aorta 
between the second and third lumbar vertebrae. 
At this level, the right renal vein also runs towards 
the caudal vena cava. 
The dorsal surfaces of both kidneys are flat- 
tened while the ventral surfaces are arched (Fig. 5- 
49). Both poles of the kidneys are rounded; the 
lateral edge is convex while the medial edge, on 
which the hilus is situated, is slightly concave. A 
longitudinal section through the kidney demon- 
strates a more triangular cut surface (Fig. 5-51). 
The right kidney is bean-shaped, and its lateral side 
is slightly bowed. The left kidney is more markedly 
curved so that the lateral wall forms a semicircle. 
The color of the kidneys is red-brown (Fig. 5- 
49), the surface is smooth and, like the Chinese 
hamster (Geyer, 1972), Syrian Golden hamster 
Schwarze and Michel, 1959-60) and rat (Wells, 
1968), each kidney contains one papilla {papilla 
renalis) (Figs. 5-50, 5-51). In sagittal section, the 
kidneys exhibit a white-gray to red-brown cortex 
about 3 mm wide, surrounded by a grayish-red 
medulla, which is from 3 to 4 times as wide as the 
cortex (Fig. 5-51). The cortical-medullary boun- 
dary is clearly defined; at this division are elevated 
interlobular vessels {aa. et vv. interlobular es) 
(Figs. 5-50, 5-51). Depending upon the nutritional 
