WE report the successful treatment of renal colic using a paravertebral subcutaneous injection of local anesthetic. The mechanism for this analgesia is unclear, but it is possibly best explained by Melzac and Wall’s “gate theory” of pain. The chief limitation of this therapy is its short duration.
A 26-yr-old woman, with an intrauterine pregnancy at 29 weeks’ gestation, presented to the emergency room of The Milton S. Hershey Medical Center reporting severe pain in the right flank. Abdominal ultrasound did not show a renal or ureteral calculus, but delayed contrast filling of the right urinary collecting system seen on an abdominal computed tomography scan was consistent with right ureteral obstruction. The patient was admitted to the obstetrics ward for pain control and observation, with plans to perform percutaneous nephrostomy if the ureteral obstruction did not resolve.
Despite administration of 150 mg meperidine and 8 mg morphine intravenously over a 4-h period, the patient reported persistent severe pain, prompting consultation with the Acute Pain Management Service. The Acute Pain Management Service performed a subcutaneous paravertebral field block in the following manner. The patient was placed in the left lateral decubitus position. Using the inferior angle of the scapula and the iliac crest as landmarks for T7 and L4 spinal levels, respectively, the T10 and L2 spinous processus were identified. After sterile preparation of the skin, a continuous subcutaneous weal of 2% lidocaine (6 ml) was created 4 cm to the right of midline, extending between T10 and L2 using a -in 25-gauge needle (fig. 1).
Before the injection, the patient reported her pain as 10 of 10 according to the visual analog scale (VAS). Five minutes after the injection, the pain was 2 of 10, and 5 min later it was 0 of 10. The patient was pain free for 2 h. Pain gradually returned, and the block was repeated when the pain score reached 7 of 10. For the second block, 6 ml bupivacaine, 0.25%, was infiltrated. Again the pain score decreased to 0 of 10 for 2 h. When the pain score reached 6 of 10, intravenous meperidine (75 mg) was administered to the patient. Two hours later, with a pain score of 1 or 2 of 10, the patient was brought to the radiology department for percutaneous nephrostomy, which was unsuccessful because of an inability to access the renal pelvis. Then, the patient was brought to the operating room for cystoscopy with ureteroscopy and ureteral stent placement during spinal anesthesia. The next day the patient was discharged free of pain with the ureteral stent in place.
We have presented a short-lived but simple, inexpensive, low-risk, and effective technique for treating pain associated with renal colic. In the United States, standard treatment for renal colic pain is administration of intravenous opioid or ketorolac. 1Side effects of nausea, pruritus, and smooth muscle spasm limit the usefulness of opioids, and the renal and gastrointestinal side effects of ketorolac are unacceptable in some patients. 2,3Alternatively, neuraxial blockade using an epidural catheter provides excellent continuous analgesia and has the advantage of the possible use of the catheter for surgical anesthesia if a stone must be extracted or destroyed. 4The small but real risk associated with placement of an epidural catheter and the side effects of epidural analgesia must be considered because 64% of pregnant patients with renal colic pass stones spontaneously. 5Although the pain relief after each paravertebral injection was superior to that provided by opioids and although the injection had no side effects, the relief lasted only 2 h. This short therapeutic effect was a limitation of the technique in this patient, but permanent results are obtained in some patients in whom pain is caused by ureteral spasm. 6The proposed mechanism for this long-lasting effect is the relief of pain-induced ureteral spasm and subsequent passage of the ureteral stone.
The mechanism whereby subcutaneous infiltration of local anesthetic blocks the pain of ureteral colic is unknown. Although the neural structure that carries the nociceptive information of renal colic from the kidney or ureter to the spinal cord and thence to the brain has not been defined clearly, the sensory innervation of the kidney and ureter occurs via diffusely organized renal, testicular (ovarian), and hypogastric plexuses. Afferent fibers travel with the sympathetic nerves and enter the spinal cord at the T10–L2 spinal nerves. 7It is difficult to conceive of a mechanism whereby this neural pathway could be blocked directly by local anesthetic that infiltrated the paravertebral subcutaneous tissue. More complicated neural circuitry must be postulated to account for the therapeutic success of the block. The duration and quality of the pain relief achieved by infiltration of 2% lidocaine and 0.25% bupivacaine were indistinguishable. If we had administered very different doses of local anesthetic, we would be able to comment on the probable mechanism of action of the drug when used in this manner. However, evidence from other studies shows that subcutaneous infiltration of water relieved renal colic, myofascial pain, and back pain during labor. 8,9
Subcutaneous field block for treatment of renal colic, as used in this patient, was described in the Soviet medical literature 6,10and is part of the standard medical practice in Russia. These descriptions report equally successful results using saline or local anesthetic infiltration. Indeed, acupuncture using needle insertion points in the paraspinous lower thoracic and upper lumbar area has been reported to control renal colic. 11,12In addition to having centuries’ worth of evidence that supports the findings of its effectiveness for the treatment of renal colic, acupuncture in this application is supported by the “gate theory” of pain. 13According to this theory, dermatomal activity in primary afferent fibers generated by performing the block or by inserting acupuncture needles would stimulate inhibitory circuits in the superficial laminae of the dorsal horn. These inhibitory neurons would prevent the transmission of nociceptive primary afferent activity from these dermatomes (the C fibers) to either local reflex arcs or ascending pain pathways. This case report supports the investigation findings regarding the effectiveness of alternative therapies for the short-term relief of renal colic pain.
The authors thank Fredrick K. Orkin, M.D., the Department of Anesthesiology, for photographic assistance; Lihua Xu, M.D., L.Ac., the Department of Internal Medicine, for assistance with traditional Chinese medicine; and Daniel P. Williams, D.O., the Department of Anesthesiology, Carol C. Coulson, M.D., the Department of Obstetrics and Gynecology, and Thomas J. Rohner Jr., M.D., the Department of Urology, for review of this manuscript. All are affiliated with The Milton S. Hershey Medical Center, The Pennsylvania State University College of Medicine, Hershey, Pennsylvania.