Contributors: Fraser McConnell

 Species: Feline   |   Classification: Miscellaneous

Introduction

Significant renal disease may be present despite radiological appearance of normal kidneys.

Radiographic considerations

  • The lateral projection is most useful for evaluation of the bladder and urethra.
  • A low KVp and high mAs should be used to maximize contrast of abdominal radiographs.
  • Care should be taken to include the entire urinary tract for most investigations.

Restraint

Indications

Ultrasonography   Ultrasonography: bladder and urinary tract  often allows a more complete evaluation of the urinary tract with the exception of the urethra for which radiography is preferred.

Radiographic anatomy

  • The kidneys and ureters are retroperitoneal.

Ureters

  • The ureters are not normally visualized unless excretory urography is performed.
  • They are less than 2 mm in diameter.
  • The ureters run in a fold of peritoneum from the renal pelvices to the trigone of the bladder.
  • The left ureter inserts into the bladder slightly caudal to the insertion of the right ureter.
  • The ureters curve cranially in a hook shape as they insert into the dorsal wall of the bladder.

Bladder

  • The bladder is situated in the caudoventral abdomen ventral to the colon.
  • It sits within the fold of peritoneum.
  • The bladder has a gently tapering neck and should lie cranial to the pelvic brim.

Urethra

  • The urethra is not normally visible on plain radiographs.
  • In males the urethra runs from bladder neck to the tip of the penis.
  • The urethra is shorter in the female.

Interpretation

  • The entire urinary tract should be on the radiograph   Abdomen: normal (fat) - radiograph lateral  .
  • Radiographs may need to be taken with the hindlimbs pulled cranially and caudally if disease of the urethra is suspected.
  • Care should be taken to assess the rest of the abdominal contents carefully for concurrent disease.
  • The lumbar spine, pelvic inlet, retroperitoneal space and sublumbar lymph nodes (which lie ventral to the 6th lumbar vertebra) should be evaluated for signs of metastatic spread of tumors.
  • Poor abdominal detail may be due to rupture of the bladder or lack of abdominal fat due to weight loss.
  • Mineralization of the renal parenchyma may be difficult to assess due to overlying fecal material in the colon.

Contrast radiography   Radiography: cystography      Radiography: double contrast cystography      Radiography: intravenous urography   is required in most cases to fully evaluate the urinary tract.

Size and position

  • In many animals in which LUTD causes pollakiuria the bladder will often be small and may difficult to delineate   Abdomen: normal - radiograph lateral  .
  • A very large bladder may indicate polydipsia, urinary obstruction, neurogenic bladder disorders or simply lack of opportunity to urinate.

Shape

  • Alteration in bladder shape is normally due to compression or displacement by adjacent structures.

Opacity

Reduced opacity

  • Gas accumulation in the bladder may be iatrogenic (previous catheterization), infection by gas-forming organisms (most commonly associated with diabetes mellitus) or over-zealous insufflation during pneumocystography.
  • Gas may also track into bladder wall and extravasate into broad ligament.

Increased opacity

  • Focal mineralized opacities within the bladder lumen   Bladder: calculi - cystogram  are most often due touroliths.
  • Usually roughly spherical and accumulate in dependent part of the bladder   Bladder: calculi - radiograph lateral  (usually the center on a lateral projection).
  • Opacity varies with composition.
  • Dystrophic mineralization- linear mineralization of bladder wall in severe chronic cystitis   Cystitis: bacterial  , neoplasia   Bladder: neoplasia  or chronic inflammation.

It is important to evaluate the entire urinary system if uroliths are detected.

Urine samples should be obtained prior to contrast studies as the contrast media will alter the results of urinalysis.

  • Nipples overlying the kidneys or bladder may be mistaken for calculi.

To identify position of nipples paint them with barium or attach a paper clip.