Ultrasound examination contraindications

General overview and advantages

Ultrasound examination (US) is a multiplanar diagnostic method characterized by wide availability and relatively low cost. A key advantage of basic ultrasound is the absence of ionizing radiation and contrast agents. This makes the method the primary tool for the initial assessment of the pelvic and abdominal organs.

In some cases, the capabilities of ultrasound may be limited. For example, visualization quality can be reduced due to bowel gas or a severe systemic condition of the patient. In such situations, the diagnostic workup is supplemented by computed tomography (CT) or magnetic resonance imaging (MRI).

Contraindications for ultrasound techniques

The provided materials do not describe direct contraindications for standard transabdominal or transvaginal scanning. However, they are clearly defined for a specialized procedure — sonohysterography.

This technique involves the placement of a balloon catheter (5F size) through the cervix followed by the instillation of sterile saline (or microbubble solution) under direct ultrasound guidance. The method is used to assess intrauterine lesions and check fallopian tube patency.

Absolute contraindications to sonohysterography:

• Pregnancy and its progression.
• Presence of active pelvic infection.

Complications of this procedure are similar to those of hysterosalpingography (HSG) and may include pain, infection, hemorrhage, and vasovagal reactions. At the same time, sonohysterography has an important advantage over HSG — it avoids radiation exposure and can be performed during a standard gynecological visit.

Application in gynecology

Transabdominal and transvaginal ultrasound (TVUS) are baseline examinations of the female reproductive system.

Main indications:

• Evaluation of pelvic pain (especially acute).
• Screening for uterine fibroids and assessment of organ enlargement.
• Investigation of postmenopausal bleeding.
• Differential diagnosis of adnexal masses.
• Guidance during invasive interventions (biopsy or drain placement).

In acute pelvic inflammatory disease (PID), ultrasound helps identify complications such as tubo-ovarian abscess or pyosalpinx. Specific ultrasound signs in this case include complex cystic masses with low-level internal echoes and layered sediment. The method also helps suspect endometriosis and pelvic varices (diagnosed when veins measure ≥4 mm in diameter with a blood flow velocity of ≤3 cm/s).

Evaluation of renal allograft and native kidneys

Ultrasound plays a critical role in nephrology and transplant medicine. A normal scan allows for accurate measurement of kidney length, ruling out focal pathology and hydronephrosis. When examining transplant recipients, native (own) kidneys must also be evaluated, as they can be a source of sepsis, nephrolithiasis, or malignancy (especially in the presence of hematuria).

Special techniques in graft evaluation:

1. Measurement of resistance indices (RIs): most informative when monitored dynamically rather than as an isolated measurement.
2. Color Doppler flow imaging (CDFI): essential for systematic measurement of intrarenal blood flow across all zones. The method is subjective but indispensable in the presence of accessory renal arteries.
3. Contrast-enhanced ultrasound (CEUS): used to assess microvascular perfusion. It measures contrast arrival time, helping to differentiate acute tubular necrosis from acute rejection (rejection prolongs arrival time).
4. Elastography: measures parenchymal stiffness and is considered a potential non-invasive alternative to biopsy.

Ultrasound diagnosis of renal abscesses

When renal or perinephric abscess is suspected, ultrasound is used for initial assessment, treatment monitoring, and drainage guidance.

On sonograms, a developing abscess appears as a hypoechoic, thick-walled mass containing internal echoes (debris). As the lesion matures, this debris may disappear, and the walls become more sharply demarcated. The kidney itself is often enlarged with deformed contours; the organ may be displaced or rotated. A perinephric abscess is visualized as a cystic mass with variable echogenicity adjacent to the parenchyma.

If gas is present within the cavity, it produces a characteristic "dirty" acoustic shadow. On Doppler imaging (CDFI/PDI), no blood flow is detected inside the abscess (it is important not to confuse mobile cellular debris with blood flow). On contrast-enhanced scans, the internal content also does not enhance, though in half of mature abscesses, the wall may show enhancement, requiring differentiation from cystic neoplasms.

Class and exam questions

What else to study on this topic

• Computed tomography (CT): indications, advantages, and risks of nephrotoxic contrast agents.
• Magnetic resonance imaging (MRI): scanning protocols, evaluation of Müllerian duct anomalies, and contraindications to gadolinium-based agents.
• Imaging of benign uterine diseases: uterine fibroids, adenomyosis, and endometriosis.
• Emphysematous pyelonephritis: risk factors, etiology, and imaging findings.
• DMSA scintigraphy: timing, signs of parenchymal scarring, and evaluation of radiopharmaceutical uptake.

Other topics in the section "Diagnostic Radiology of the Abdominal Organs"

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