Pyelography: X-ray of the kidneys with contrast, indications

Pyelography is a general term for contrast studies of the renal pelvis and ureters, which are performed to detect obstruction, filling defects, fistulas, urinary leaks, and other urodynamic abnormalities. In modern practice, the term encompasses intravenous urography, retrograde pyelography, and antegrade pyelography, as well as their role alongside computed tomography and magnetic resonance imaging of the urinary tract. [1]

Over the past decade, computed tomography (CT) urography has become the first-choice method for the initial evaluation of macrohematuria and many urological complaints, while intravenous urography (IVU) has lost its position as a first-line method and is used for more specific indications. This is reflected in current appropriateness criteria and clinical algorithms for urological imaging. [2]

Types of pyelography and how they differ

Intravenous urography (IVU) involves the intravenous administration of an iodinated contrast agent with sequential radiography as it is excreted by the kidneys. This method reveals the anatomy of the renal pelvis and ureters, detecting contrast retention and filling defects, but has gradually given way to tomographic methods. [3]

Retrograde pyelography is performed during cystoscopy: a catheter is inserted into the ureteral orifice and, under fluoroscopic guidance, contrast is injected for detailed lumen profiling. This method is particularly useful in cases of obstruction, suspected tumor, planning stenting and ureteroscopy, and trauma. [4]

Antegrade pyelography is performed through a nephrostomy access when retrograde advancement is impossible or contraindicated. It is used to determine the level of blockage, ureteral patency, and to determine drainage or stenting strategies in complex clinical situations. [5]

Table 1. Pyelography options

Option	Key goal	Typical context
Intravenous urography	General anatomy and excretory function	Limited scenarios where tomography is not available
Retrograde pyelography	Target contour of the ureteral lumen	Obstruction, stent planning, trauma
Antegrade pyelography	Assessment of patency from a nephrostomy	High block levels, retrograde access failure

The classification and roles of methods correspond to modern review materials and practical guidelines. [6]

When prescribed: indications according to clinical scenarios

In cases of macro- or microhematuria, computed tomography urography is often the primary method, while intravenous urography is considered less appropriate. Retrograde pyelography remains useful in cases of inconclusive CT scans or for intraoperative lumen verification. [7]

In cases of obstruction, retrograde pyelography helps localize the blockage level, assess the filling defect, and immediately perform stenting. In cases where retrograde access is impossible, antegrade pyelography and antegrade stenting are performed through a nephrostomy access. [8]

In ureteral trauma, retrograde pyelography provides direct visualization of the site of leak or contrast interruption, however, in multifactorial injuries, the assessment begins with computed tomography with a urographic phase, according to specialized recommendations. [9]

In oncourology and preoperative planning, retrograde pyelography is used as a complementary method to tomographic examinations, improving the accuracy of lumen mapping for biopsy and endoscopic interventions. In a number of situations, computed tomography urography has demonstrated comparable diagnostic value to retrograde pyelography for the upper urinary tract. [10]

Table 2. Scenarios and preferred methods

Scenario	Preferably	The role of pyelography
Macrohematuria	Computed tomography urography	Intravenous urography is not generally recommended.
Descending obstruction	Retrograde pyelography	Block localization and stenting
High block, nephrostomy	Antegrade pyelography	Patency confirmation and antegrade stent
Ureteral injury	Computed tomography urography	Retrograde pyelography to clarify the defect

Positions on the choice of methods reflect the consensus of guidelines and review articles on urologic imaging.[11]

Contraindications and restrictions

Any pyelography involves the administration of iodinated contrast and therefore requires an assessment of the risk of hypersensitivity, post-contrast acute kidney injury, and extravasation. The current edition of the guidelines on contrast agents emphasizes risk stratification and individualized prophylaxis. [12]

During pregnancy and in children, radiation-sparing strategies are used, avoiding ionizing radiation when the clinical issue can be addressed with alternatives. For children, there are separate recommendations for the safe use of contrast media and the prevention of acute kidney injury. [13]

In severe acute pyelonephritis, when therapy is ineffective, transverse tomography methods are recommended, since they are better at identifying complications than routine projection studies. [14]

Retrograde pyelography is not performed in cases of uncontrolled urinary tract infection and severe pain without adequate analgosedation, as the procedure may increase intrarenal pressure and the risk of bacterial translocation effect. [15]

Table 3. Key contraindications and what to do instead

Situation	Limitation	A safer alternative
High risk of contrast reaction	Iodine-containing contrast	Selection of low-osmolar contrast, premedication, alternative methods
Pregnancy at low urgency	Ionizing radiation	Ultrasound, magnetic resonance imaging if necessary
Active infection and fever	Risk of urosepsis with retrograde pressure increase	Delay and antibacterial therapy, drainage as indicated
Severe reduction in glomerular filtration rate	Risk of post-contrast kidney injury	Individual risk assessment, hydration, alternative imaging

The strategies are consistent with current contrast media safety documents and urological guidelines. [16]

Patient Preparation: Before, During, and After

Before an intravenous urogram, the doctor will review the patient's allergy history, concomitant illnesses, and medications. If necessary, they will recommend a light bowel preparation and restrictions on food and drink the day before. The procedure and possible discomfort will be explained to the patient. [17]

Before retrograde pyelography, it is important to exclude active urinary tract infection, assess the risk of difficulty catheterizing the ostium, and plan for possible stenting. In some observational groups, hydronephrosis and the absence of prophylactic antibiotics in high-risk patients were predictors of postoperative infection. [18]

In the presence of a nephrostomy, antegrade pyelography is performed through the installed drain with careful contrast administration under fluoroscopic guidance, allowing for assessment of ureteral canalization and planning of further steps. The standard includes recording the achieved level and pattern of contrast flow. [19]

Following any contrast procedure, patients are advised to maintain adequate hydration, monitor symptoms, and seek immediate medical attention if they experience fever, chills, severe pain, or signs of an allergic reaction. These general measures reduce the risk of late adverse events and recurrence. [20]

Table 4. Preparation checklist

Stage	What to check	For what
Before the study	Allergies, concomitant diseases, medications	Reducing the risk of contrast reactions
On the day of the procedure	Hydration, no active infection	Prevention of complications
In the office	Agreement, explanation of sensations and stop signals	Safety and compliance
After	Instructions for hydration and anxiety symptoms	Early identification of complications

The checklist items are consistent with current patient materials and professional recommendations. [21]

How to do it: a brief overview of the technique

In intravenous urography, contrast is injected into a vein, followed by a series of images of the abdomen and pelvis, assessing the contrast's progress through the renal pelvis and ureters, documenting delays, defects, and asymmetries in excretion. Protocol options are adapted to the clinical question. [22]

Retrograde pyelography involves catheterization of the ureteral orifice under cystoscopic guidance and slow injection of contrast agent, with real-time visualization of the lumen. The procedure is often combined with diagnostic ureteroscopy, biopsy, and stenting, as indicated. [23]

Antegrade pyelography is performed through a nephrostomy catheter, allowing for assessment of patency from the upper section when a retrograde approach is impossible. This method is indispensable in drainage algorithms for high blockages and in onco-urological situations. [24]

What it shows and how it is interpreted

Pyelography reveals filling defects due to stones and tumors, parietal defects due to strictures, stepwise transitions due to external compression, and extravasation due to trauma or suture failure. When assessing the upper urinary tract, computed tomography urography is comparable in diagnostic accuracy to retrograde pyelography in some groups. [25]

In situations following ureteral surgery, pyelography allows for objective confirmation of anastomotic integrity and the absence of leakage. In oncology, it helps determine the extent of lumen damage and determine the trajectory of the biopsy instrument. [26]

Table 5. Typical radiographic signs and their interpretation

Find	Probable nature	Practical tactics
Round filling defect	Stone or tumor	Correlation with tomography, ureteroscopy according to indications
Uneven parietal defect	Stricture or inflammation	Dilation or reconstruction as indicated
Rupture of contours with extravasation	Injury or failure	Immediate drainage and correction
Persistent contrast delay	Block level	Drainage, stenting, determining the cause

The tabular features summarize the clinical and radiological experience and the provisions of review publications. [27]

Safety and radiation exposure

Computed tomography urography typically delivers a higher effective dose than traditional urography, but modern dose-saving protocols, including split contrast administration, significantly reduce the burden without sacrificing diagnostic quality. Comparison of methods also requires consideration of the benefits of a comprehensive assessment of the abdominal cavity. [28]

For orientation, patients can benefit from a comparison with natural background radiation: the average annual dose of natural radiation is approximately 3 mSv, which helps understand the relative magnitude of medical doses. Specific values for pyelography depend on the number of series, the equipment, and the patient's constitution. [29]

Table 6. Dose guidelines and how to reduce them

Study	Dose trend	What reduces the dose?
Traditional urography	Lower than standard CT urography	Collimation, minimum series
Computed tomography urography	Higher, but optimizable	Split bolus, low-dose protocols
Retrograde pyelography	Low, time-dependent fluoroscopy	Pulsed fluoroscopy, time limit

The data reflect the general conclusions of research and educational materials on the safety of radiation diagnostics. [30]

Contrast: risks, prevention, special groups

Contrast media guidelines highlight two key safety areas: hypersensitivity and post-contrast acute kidney injury. The approach includes a thorough history, risk stratification, discussion of premedication, and, if necessary, selection of an alternative agent. [31]

In children, separate protocols are used to assess the risk of post-contrast renal injury, taking into account congenital anomalies, prematurity, and drug factors. The decision to administer an injection is always weighed against the diagnostic value and the availability of alternatives. [32]

Table 7. Risk stratification for contrast administration

Risk	Factors	Prevention
Hypersensitivity	Previous reaction, atopy	Premedication, agent change, reaction treatment readiness
Post-contrast renal injury	Low glomerular filtration rate, dehydration	Hydration, adjustment of nephrotoxic drugs
Extravasation	Difficult venous access	Visual control, immediate stop if pain occurs

The points are consistent with the practical recommendations for contrast safety. [33]

Complications of retrograde and antegrade pyelography and how to minimize them

Urinary tract infections have been reported following retrograde pyelography; significant predictors include severe hydronephrosis and lack of antibacterial prophylaxis in high-risk patients. The decision on prophylactic antibiotics is made by the urologist, taking into account the local resistance profile. [34]

Retrograde manipulations pose a risk of increased intrarenal pressure, which can lead to pyelorenal reflux and urosepsis. Controlling irrigation pressure and time, as well as limiting the volume of contrast, reduces this risk. [35]

After antegrade procedures, complications and their prevention tactics depend on the indications for nephrostomy, the state of the drainage tract and concomitant infection; pyelography through the nephrostomy helps to promptly recognize patency problems. [36]

Table 8. Frequent complications and prevention

Procedure	Complication	What reduces the risk
Retrograde pyelography	Urinary tract infection	Infection screening, selective prophylaxis, gentle technique
Retrograde pyelography	Pain and spasm	Adequate analgosedation, slow administration
Antegrade pyelography	Extravasation	Pressure control, correct positioning of the catheter
Any	Reaction to contrast	Risk stratification, emergency preparedness

The summary is based on current clinical series and guidelines.[37]

Comparison with tomographic methods and choice of tactics

Computed tomography urography is the first-line method for hematuria and many urologic scenarios due to its high sensitivity for tumors and stones, as well as the ability to simultaneously evaluate other abdominal and pelvic organs. Intravenous urography is generally less appropriate in these situations. [38]

Magnetic resonance urography is used when iodinated contrast is contraindicated, in pediatrics and pregnancy for strict indications, and to assess functional aspects without ionizing radiation. Retrograde and antegrade pyelography retain their value as targeted intraoperative and definitive methods in cases of complex obstruction. [39]

Table 9. How to choose a method for a clinical question

Clinical question	Preferred method	The role of pyelography
Identifying the source of macrohematuria	Computed tomography urography	Targeted supplement for questionable finds
Block level confirmation	Retrograde pyelography	Immediate stenting when indicated
Retrograde access failure	Antegrade pyelography	Patency assessment and antegrade stent
Contraindications to iodine contrast	Magnetic resonance urography	Avoiding radiation and iodine

The comparison reflects clinical relevance algorithms and review data.[40]

A short algorithm for practice

Step 1. Determine the clinical question. For hematuria, consider computed tomography urography as the initial modality according to the criteria for appropriateness. [41]

Step 2. In case of obstruction, choose retrograde pyelography to confirm the level and perform immediate intervention; if passage is impossible, plan antegrade pyelography through a nephrostomy. [42]

Step 3. Before contrast administration, assess the risk of hypersensitivity and post-contrast renal injury, as well as the appropriateness of prophylactic antibiotics in patients at high risk of infection. [43]