Urography

Voelker and Lichtenberg developed radiological diagnostics of the urogenital tract from 1905 and introduced retrograde pyelography (Peters 1991). It had already been known since 1896 that iodine has contrasting properties. Radiographic imaging of the urinary tract with iodine salts was first reported by Osborne, Sutherland, Scholl, and Rowntree in 1923. The contrast imaging met the expectations, but because of the high toxicity this examination method had to be abandoned again (Maurer 1991).

In 1925, A. Binz and C. Räth synthesized a pyridine compound (oxipyridine) which partially contained iodine, but only Swick succeeded in 1928 - 1929 in developing Selectan neutral and Uroselectan, respectively, which made the toxic iodine well tolerated. Since then, i. v. excretion urography could be used as a routine method (Peters 1991).

Urography is one of the imaging procedures in urology and nephrology.

It is an X-ray examination performed with an iodine-containing contrast medium.

The iodine-containing contrast medium is filtered glomerularly and neither secreted nor reabsorbed tubularly. Therefore, the renal parenchyma can be well visualized at the highest possible contrast medium concentrations in the primary urine. This is the case approximately 1 - 3 min after bolus injection (Kuhlmann 2015).

Urography used to be the standard procedure for imaging the draining urinary tract and residual urine (Kuhlmann 2015), but it has now been increasingly displaced by CT, as both sensitivity and specificity are significantly higher with CT (Manski 2019).

Nowadays, urography is generally only used when sonography and / or CT are not available (Herold 2018).

The imaging technique depends on the problem and also on the renal function.

It can be depicted:

• Kidney size
• configuration of the kidney
• possible indications of obstruction
• anatomical anomalies such as:
  • cysts
  • medullary sponge kidneys
  • lesions of the papillae
  • tumors
• residual urine formation
• changes in the lesser pelvis
• Anatomical changes in the area of the hollow system of the kidneys (Kuhlmann 2015).

Indications for urography are:

• Renal colic
• recurrent urinary tract infections
• Macrohematuria
• Nephrolithiasis
• Urinary retention
• Trauma of the kidney
• Malformations of the urinary tract
• Urothelial carcinomas (Manski 2019)

Premedication:

To mitigate the risk of an allergic reaction in patients with a history of known contrast reactions, atopy, or asthma, the following premedication is recommended:

• Prednisolone 30 mg p.o. 12 h, 6 h and 1 h before administration of KM.
• Fenistil 1 mg p. o. 12 h and 1 h before administration of KM
• Cimetidine 200 mg p.o. 12 h and 1 h before administration of KM

or as intravenous administration immediately before administration of KM:

• Fenistil 0.1 mg/kg bw slowly i.v.
• Cimetidine 200 mg slow i.v.
• Prednisolone 100 mg i. v. (whereby oral administration of prednisolone at a time interval from the examination offers better protection) (Manski 2019).

Procedure:

Before administration of the contrast medium, an abdominal overview image is taken with an empty urinary bladder, then the KM is administered as an infusion with a concentration of 1 - 1.5 ml / kg bw and a concentration of 300 mg / ml iodine as a short infusion.

A further abdominal overview image initially shows the flooding of the contrast medium.

The image taken 2 - 3 min after administration of KM is referred to as the "nephrographic phase", in which the renal parenchyma can be best visualized. Normally, both kidneys appear in the same intensity, parenchymal defects are not detectable, the kidney length is 11 cm - 12 cm, the width is about 5 cm and the parenchymal thickness is 2 cm - 3 cm.

Further images are taken after 6 min (for visualization of the renal pelvic calices and the proximal ureters) or after 12 min (in this case there is normally a lateral contrast of the ureters and the urinary bladder). Any segmental stenoses are usually signs of peristalsis. The diameter of the ureter should be < 8 mm cranially to the stenosis.

In case of signs of urinary retention, lack of sufficient bladder filling or special questions, late images (1 - 2 h after administration of KM) can be taken to document KM outflow and bladder emptying. (Manski 2019)

If special focus is placed on the renal pelvicocaliceal system during radiographic imaging, special abdominal belts can be placed on the patient to compress the ureters in the first few minutes (Manski 2019).

If the urine outflow is obstructed (e.g. by a ureteral stone), there is an increase in pressure in the renal pelvic caliceal system during urography due to the increase in diuresis caused by the BM and thus the risk of fornix rupture. For this reason, urography should not be performed in the presence of colic.

If a fornix rupture occurs, the insertion of a ureteral splint is required in addition to antibiosis (Manski 2019).

1. Herold G et al (2018) Internal medicine. Herold Publishers 605, 657
2. Kuhlmann U et al. (2015) Nephrology: pathophysiology - clinic - renal replacement procedures. Thieme Verlag 57, 542
3. Manski D (2019) The urology textbook. Dirk Manski Publishers 110 - 115
4. Maurer H J (1991) Historical overview of the development of iodinated X-ray contrast media. In: Peters P E , Zeitler E (eds) X-ray contrast media. Springer, Berlin, Heidelberg.1 - 4 https://doi.org/10.1007/978-3-642-76338-0_1.
5. Peters P E et al (1991) X-ray contrast media: side effects - prophylaxis - therapy. Springer Verlag 1 - 5