Interventional Ultrasound: US-Guided Puncture of the Bladder

Fig. 29.1

Ultrasound probe with puncture adaptor

The bladder must be well distended to ensure an optimal view (more than 300 ml), so that the bladder dome is palpable at least 5 cm above the pubic symphysis [16] (Fig. 29.2).

Fig. 29.2

Suprapubic bladder ultrasound

In patients who do not suffer from urinary retention, the distension can be achieved by filling the bladder with saline solution through a ureteral catheter or in particular cases during cystoscopy.

Transabdominal US allows the bladder to be examined on the longitudinal and transverse planes, showing the margins, the degree of filling, the viscera, and the catheterization region. In transverse scanning the probe is positioned parallel to the pubic symphysis and the needle in medial position to the probe: it will appear as a luminous dot. Moving the probe from side to side can make it easier to see the needle, even if in this scan the needle may often be pushed beyond the correct location because of the difficulty in visualizing the point due to echo artifacts. In longitudinal scanning the probe is placed sagittally. The needle is pushed forward through the end of the probe, and so the needle point, needle, and course are visible at all times (Fig. 29.3).

Fig. 29.3

Placing the needle during the maneuver (shadow)

In most cases, the bladder content is anechogenic; in patients already fitted with a catheter, there may sometimes be air inside the bladder that will appear as a hyperechogenic area in the bladder dome. The small intestine, unless it contains gas, will appear as a circular or linear compressible image. However, it should be borne in mind that only some authors have claimed that the ultrasound device is reliable in excluding the presence of a bowel loop in the suprapubic region [4, 17, 18].

Once the reference points have been identified (the peritoneal reflection, the pubic symphysis, and the best point for bladder puncture), after preparing the skin, a sterile drape is placed through which an opening will be created at the level of the incision zone.

29.4 Positioning Technique

The puncture site is generally 2–4 cm above the pubic symphysis. In obese patients it is advisable to position the Cystofix above the skinfold in the suprapubic region, to reduce the risk of local infections and dermatitis.

The needle must be angled at 60–90° to the abdominal wall, to make sure that the catheter balloon does not rest on the trigone.

The procedure must be performed under local anesthesia infiltrating sufficient anesthetic (typically between 5 and 20 ml of 1 % lidocaine) to cover the calculated course of the catheter; more rarely, intravenous sedation may be administered (midazolam 2.5–5 mg) or regional or general anesthesia. In the specific case of a patient with a spinal cord injury at level T6 or above, local anesthesia is not enough to prevent a possible dysreflexia.

Antibiotic prophylaxis is always advisable to reduce the risk of infection [19], also bearing in mind that in long-term bearers of a catheter, colonization of the urine with antibiotic-multiresistant bacteria is very probable. Moreover, interruption or modification of the anticoagulant or antiaggregant therapy is recommended, to reduce the risk of bleeding.

On the market, various kits are available that can be used for the catheterization procedure: those for direct puncture (Fig. 29.4) or those for drainage with the Seldinger technique [20].

Fig. 29.4

Suprapubic catheter placement kit

Direct puncture involves piercing the bladder at the suprapubic level, under US guidance, with a metal stylet of a suitable caliber, to be positioned in the bladder lumen. When urine is seen to flow, the drainage tube is inserted in the stiletto caliber, which is easily visible at US scanning (Fig. 29.5). The drainage is anchored with silk stitches to the skin and connected to a urine collection bag (Fig. 29.6).

Fig. 29.5

Drainage tube in the bladder (shadow)

Fig. 29.6

Suprapubic catheter in place after the procedure

The Seldinger technique is the safest for inserting a suprapubic catheter. Once the needle has been positioned (mean caliber 1.2 mm) in the bladder under US guidance, the rigid Lunderquist-type guidewire with a soft point is introduced (mean caliber 0.7 mm) and the needle is withdrawn. At this point urine flow should be observed, confirming the correct position, and the skin incision area can be widened with a triangular scalpel blade.

On the guidewire, progressive dilators up to a maximum of 12 F are fitted. The dilation must be achieved by sliding the dilators along the guidewire with a gentle “screwing” type maneuver. Excessive tension will increase the risk of twisting the guidewire and damaging the bladder. During the maneuver, it is necessary to ensure that the dilator sheath follows the line of the guidewire at all times and the thread remains free.

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