Radiological examination of urinary organs

Peculiarities of the structure of kidneys in children:

1) Relatively large size
2) lobular structure
3) low topographic position
4) round shape
5) high mobility
6) medullary layer is larger than cortical
7) wide renal pelvis

Methods of radiological examination

Radiological examination is the leading one in Urology. It helps to check morphological and functional changes in urinary organs.

·        Plain radiography is used to detect stones in urinary tracts and calcinosis. Shades of kidneys are visible, so the size and position of them can also be described.

·        Radiological examination with contrast — the main method of examination of hollow organs: pelvises, urinary bladder, urethra. Contrast examination helps to assess anatomical and functional condition of urinary organs. Contrast substances: iodine-containing solutions and gas (air, oxygen).

·        Retrograde urography (pyelography) — a contrast examination of urinary tracts by introducing contrast substance via catheters in ureters.

·        Cystography — contrast substance is introduced into the urinary bladder and radiography is done.

·         Pneumopyeloureterography — contrast examination of pelvises and ureters, when they are filled with air or oxygen. It is done to detect non-opaque stones (urates).

·        Intravenous (excretory) urography – after 20-60 ml of water solution of contrast substance are introduced intravenously, radiography is done every 5 minutes. The position of the patient can be horizontal or vertical. It allows to assess the condition of urinary tracts, secretory and excretory function of kidneys and is used for diagnosis of many diseases.

Abnormalities of kidney development

Abnomalies of “quantity” make up 31% of all kidney abnormalities. This group includes agenesis and aplasia, duplication of the kidney and an additional (third) kidney.

The most frequent of them (more than 70% of all quantity abnomalies) is a duplication of the kidney.

Agenesis is a complete absence of a kidney. In every fourth patient, renal agenesis is combined with an abnormality of male genital organs.
In case of aplasia, a rudimentary vascular pedicle and a lump of parenchyma about 3 × 2 cm in size are detected. Such kidney does not have a pelvis and does not produce urine.

A characteristic symptom of aplasia and agenesis of the kidney, detected with the help of cystoscopy, is absence of the ostium of the ureter and the corresponding half of the bladder. It is clear that in excretory urograms, the shade of not only a functioning kidney, but also the renal pelvis, is enlargered, because twice the amount of urine passes through it. Angiography is a method for diagnosing renal agenesis and aplasia.

Kidney duplication can be complete and incomplete. In case of complete duplication, each half of the kidney has is a separate pyelocaliceal system - in the lower one it is developed normally, and in the upper one it is underdeveloped. The ureter starts from each pelvis. Duplication of the parenchyma and blood vessels of the kidney without duplication of the pelvis should be considered incomplete duplication of the kidney.

Duplication of the kidney is easily detected by excretory urography (X-ray method with contrast, which is administered intravenously). If there are doubts, it is recommended to perform selective renal arteriography.

Additional (third) kidney. The additional kidney lies separately from the main one, it is less than normal (in size), but it functions normally.
Additional kidney is extremely rare. It is found during an examination for similar diseases or by chance — with excretory urography, retrograde pyelo-, angiography or sectional examination. Usually, such kidney is removed.

Kidney abnormalities

    • Hypoplasia of the kidney. It is believed, that the kidney is underdeveloped due to a decrease in the caliber of the renal artery.

Hypoplasia of the kidney does not have specific symptoms. It is detected by means of excretory urography, ultrasound, retrograde pyelography. At the same time, attention is paid to a decrease in the size of a kidney itself and its pyelocaliceal system. If differential diagnosis of hypoplasia and secondary nephrosclerosis is confusing, renal arteriography is performed, which reveals a gradual decrease in the diameter of the renal vessels in the first case, fast and uneven in the second.

Kidney location abnormalities
The frequency of abnomalies in the location (dystopia) of the kidney is 1 in 800 autopsies. The cause of renal dystopia is seen as a violation of the growth of the ureter and blood vessels while the kidney is moving to its usual location in the lumbar region. The main feature of dystopia is an incorrect position of the kidneys in relation to the skeleton.

Dystopia can be unilateral (homolateral) and bilateral (heterolateral). Kidneys can lie in the lumbar or iliac region, in the pelvic cavity. Thoracic dystopia is less common than others. Dystopia is called heterolateral, when the kidneys are displaced beyond the midline of the body.
An excretory urography or renal scintigraphy allows you to make the correct diagnosis and avoid unnecessary surgery (kidney scans are performed after contrast is introduced.)

Kidney relation abnormalities
In most cases lower poles of kidneys are fused, forming a horseshoe-shaped kidney. If opposite poles of kidneys are fused, the result is an S-shaped (directions of pelvis and ureter are opposite) or L-shaped (directions of pelvis and ureter are the same) kidney.

Abnomalies of the structure of the kidney

In clinical practice, polycystosis and a single (solitary) cyst of the kidney are more frequent than others; medullary sponge kidney, multicystosis, rudimentary and dwarf kidneys, etc. are much less common.
Kidney dysplasia. A distinctive feature of kidney dysplasia is a sharp decrease in its size and the abnormal structure of the parenchyma, causing dysfunction. There are two variants of this deviation from the norm -  rudimentary and dwarf kidneys.

To detect such abnormalities, ultrasound of the kidney, excretory urography, radiorenography and scintigraphy, selective renal arteriography are necessary. The treatment is only surgical.

Simple (solitary) kidney cyst.

It is a single round cystic mass with a diameter of 10 cm or more on the surface of the kidney in any part of it, containing a transparent opalescent or hemorrhagic fluid.

A simple cyst can be detected by ultrasound and x-ray examination
In a renal arteriogram, the cyst looks like an avascular round area, and it can be easily differentiated from kidney cancer.

Polycystic kidney disease - the presence of many cysts of different size on the surface and in both kidneys. Between them, sections of the unchanged parenchyma are preserved.

With the help of ultrasound and urography, enlargement of both kidneys is clearly visible. The renal pelvis is compressed and elongated. The calyces are bulb-shaped and widened, and their necks are long.

Urolithiasis

·Diagnosis of urolithiasis is not possible without a plain radiography. If a stone is visible in an X-ray image, it is  radiopaque, and even the type of the stone can be assumed. X-ray examination allows to assess the exact size, shape, position of stones. Pure urate and cystine stones are  non-radiopaque and poorly visible in an X-ray image or not visible at all.

· Excretory urography gives a clear image of ​​the anatomical condition of the kidneys and the location of the stone, indirectly indicating their functional condition, as well as the functional condition of the upper and lower urinary tract. Timeliness (7-10 min) of accumulation of a contrast substance in the kidney with visualization of the pyelocaliceal system allows us to assess their functional condition, determine the type of pelvis (intra- and extrarenal type), the degree of retention (expansion) of the pyelocaliceal system. The shade of the stone is a defect in contrasting of the urinary system.

· Excretory urography is not informative for non-radiopaque ureter stones, the exception is cases of stasis above an obstruction due to a ureter tumor. In those rare cases when the diagnosis after the examination remains doubtful or the shade of the stone is not visible, retrograde ureteropyelography is done.

Hydronephrosis

Hydronephrosis (from Greek hydro-water and nephros - kidney) is a persistent, progressive expansion of the renal pelvis and calyces, associated with impaired outflow of urine from the kidney, which leads to gradual thinning and atrophy (hypotrophy) of the renal parenchyma. Hydronephrosis can be in both children and adults. In most cases hydronephrosis affects one kidney, but it can also be bilateral.

Radiological methods of examination in case of hydronephrosis:

• Plain urography. In a plain X-ray image, enlargement of a kidney can be  detected, as well as the presence of stones in the projection of the urinary system;

• Excretory urography (intravenous urography) — accumulation of contrast substance in the affected kidney may be delayed due to impaired function; there can be a significant expansion of the kidney cavities (pelvis, calyx), thinning of the parenchyma, psoas symptom, narrowing of the pyelourethral segment, possible presence of stones in the projections of the urinary system, cysts, tumors, narrowing of the distal ureter, etc.

Kidney tumors

Tumors of the renal parenchyma and tumors of the pelvis differ in both structure and ways of spreading and require various diagnostic and treatment methods.

Renal Parenchyma Tumors

a) Benign tumors: adenoma, lipoma, fibroma, myoma, angioma and hemangioma, lymphangioma, myxoma, dermoid.

b) Malignant: renal cell carcinoma, fibro-, myo-, lipo-, angiosarcomas, mixed Wilms tumor (in children).

c) Secondary (metastatic) kidney tumor.

Tumors of the renal pelvis

a) Benign tumors: papilloma, angioma, leiomyoma.

b) Malignant tumors: transitional cell carcinoma, squamous cell carcinoma, mucoglandular cancer, sarcoma.

Hypernephroma

Hypernephroma (adenocarcinoma, Gravitz tumor, hypernephroid cancer) makes up about 2-5% of malignant neoplasms in general, and in urology - up to 85% of all cases of kidney cancer. The triad of symptoms in patients with kidney cancer: pain, palpable tumor, hematuria.

X-ray signs of a kidney tumor: an increase in the size of the kidney, a filling defect of the pelvis and calyces, their deformation and spreading. Angiography determines a deformation and destruction of arterial branches of the 1st and 2nd order in the tumor area, accumulation of contrast substance in the vessels of the tumor in the form of spots, "puddles".