Curative efficacy of low frequency electrical stimulation in preventing urinary retention after cervical cancer operation

Cervical cancer is the most common gynecologic malignant tumor, and extensive panhysterectomy is a radical surgery for the treatment of cervical cancer. The wide range of surgical resections (including the uterus, fallopian tube, the upper part of the vagina, the main ligament, and the paracolpium) and the complete dissection of the pelvic lymph nodes often brings a number of postoperative complications such as bladder dysfunction (anesthesia, urinary incontinence, and urinary retention), lymph cyst, lymphedema, ureterovaginal fistula, intestinal obstruction, wound infection, and urinary tract infections, in which bladder dysfunction is the most common [1]. The incidence of bladder dysfunctions after radical hysterectomy for cervical cancer is 8.0–80% [2, 3]. Postoperative urinary retention can lead to the excessive expansion of the bladder or even permanent detrusor damage, and preventing urinary retention through an indwelling catheter may bring pain and inconvenience to the patient, increasing the incidence of urinary tract infection [4, 5]. In recent years, some scholars have begun to apply electrical stimulation for postoperative rehabilitation of malignant tumors, effectively improving the quality of life of patients. Mariotti et al. randomly divided 60 patients with prostate cancer into two groups according to 1:1. The treatment group received pelvic floor electrical stimulation on the seventh day after the operation, and the control group received routine nursing treatment. Postoperative follow-up showed that the urination function of the treatment group was significantly better than that of the control group [6]. In terms of gynecologic malignancies, Eun et al. randomized 34 patients with gynecologic malignancies to two groups; the electrical stimulation group received 4 weeks of electrical stimulation, and the control group received conventional treatment. The quality of life questionnaire showed that the quality of life and pelvic floor function of the patients in the electrical stimulation group were significantly better than those in the control group [7]. At present, there are few studies on the rehabilitation treatment of urinary retention electrical stimulation after cervical cancer surgery. Based on the previous studies, we will fill in the gaps in related research fields and provide effective treatment methods for improving the postoperative quality of life of patients with cervical cancer.

In general information, the differences in age, culture degree, the number of pregnancies and deliveries, weight, and clinical staging of cervical cancer between patients in these two groups were not statistically significant.

As shown in Table 1, after removal of the catheter, bladder residual urine volume was significantly lower in patients in the electrical stimulation group than in the control group (F = 1.087, P = 0.000), and the difference was statistically significant.

As shown in Table 2, the difference in postoperative fever days of patients and antibiotic use days between the two groups was not significant, and P values were 0.818 and 0.754, respectively. At the beginning and end of the postoperative treatment intervention (11th and 14th day, respectively), the routine urine test was conducted to observe whether patients developed urinary tract infection and was expressed as the leukocyte count. There was no significant difference in urinary tract infection between the two groups, and P values were 0.229 and 0.500, respectively.

As shown in Table 3, the incidence of urinary retention was significantly higher in the control group than in the electric stimulation treatment group (P = 0.000).

As shown in Table 4, the difference was not statistically significant between the two groups with different parameters (P = 0.782), but the incidence of urinary retention in group B was lower than in group A (9.09% < 11.54%). This prompts that the treatment effect in the endorphins analgesia program is better compared with that in the neuromuscular repair program.

As shown in Table 5, the levels of muscle strength in the group of bladder training and electrical stimulation before and after the intervention underwent paired t test. It was found that all types of muscle fibers of the pelvic floor were statistically significant (P < 0.05), suggesting that low-frequency electrical stimulation can enhance pelvic floor muscle strength.

When patients with cervical cancer undergo extensive panhysterectomy and pelvic lymph node dissection, some of them would develop urinary retention. The reason is damage to the pelvic fascia, ligaments, pelvic support tissue, blood vessels, lymphatic vessels, and nerves during the operation, resulting in bladder dysfunction; thus, urinary retention is one of the earliest and most common causes of great sufferings. Its pathogenetic mechanism is as follows. The inferior hypogastric plexus bladder branch contains sympathetic and parasympathetic nerve fibers, which controls the sphincter and detrusor of the bladder, respectively, perceives bladder volume changes, and mutually regulates this to control urination. Parasympathetic nerve injury can reduce bladder sensitivity to pressure, leading to urinary retention. Thus, damage to the pelvic floor support structure leads to a downward position of the vaginal fornix and urethra and emptiness behind the bladder. The bladder in the filling state falls back due to the loss of support strength, excessively stretching towards the sacrum fossa; thus, the bottom of the bladder and posterior length of the urethra forms an acute angle, resulting in the accumulation of urine in the bladder. Bladder neck obstruction can also easily lead to urinary retention. Some patients develop pelvic inflammation and adhesion, which result in muscle tension and failure to urinate, leading to varying degrees of urination disorders [11‐14].

In the 1970s, Tanagho et al. first applied the electrical nerve stimulation technique in the treatment of patients with bladder dysfunction through direct electrical stimulation on neural pathways influencing the bladder detrusor, promoting the recovery of sacral nerve function, which adjusts bladder function [15]. In 1997, sacral nerve electrical stimulation treatment was certificated by the FDA for the treatment of unstable bladder and non-obstructive urinary retention [16]. Peters et al. reported that in the treatment of primary urinary retention using sacral nerve stimulation, improvement of symptoms was up to 73% [17]. Kajbafzadeh et al. used transcutaneous functional electrical stimulation (FES) to treat children with refractory neurogenic urinary incontinence secondary to myelomeningocele (MMC) and found that FES was a safe, non-invasive, and effective method compared with the control group [18]. The possible mechanism may be as follows. The second, third, and fourth sacral nerves control bladder function, in which these nerves grow from the root of the third sacral nerve and are mainly distributed in the detrusor of the bladder and pelvic floor levator ani muscle. The root of the third sacral nerve contains the sensory plexus from the pelvic floor and motor plexus from the detrusor (parasympathetic), as well as motor plexuses from the sphincter and other muscles. Effective electrical stimulation on the third sacral nerve can provide a curative effect through the regulation of the urination reflex mediated by the afferent nerve, promoting the recovery of bladder sensation and establishing a normal urination reflex at the same time. In recent years, many studies have reported that after surgery, pelvic floor nerve electrical stimulation could promote the recovery of bladder function, which brought a good curative effect [19, 20].

In the past, in order to avoid the occurrence of urinary retention, the common method was as follows: 3 days of bladder function training was performed before the removal of the catheter on the 14th day after surgery, but this effect was limited. Through the randomized controlled study, our hospital data revealed that the incidence of urinary retention in the control group was 46.51%. From the above treatment principle, the following treatment method was adopted in our hospital: in addition to bladder function training 3 days before the removal of the catheter, low-frequency electric stimulation treatment is performed. This treatment method significantly reduced the incidence of urinary retention, reaching 10.41%; which indicate that low-frequency electric stimulation also can significantly reduce the incidence of urinary retention after cervical cancer operation. This is of great practical significance to the rehabilitation and improvement of the quality of life after surgery.

For the treatment of cervical cancer patients with urinary retention after extensive panhysterectomy, the principle of low-frequency electrical stimulation is as follows. Through electrodes placed on abdominal skin, pulsed current functions as a stimulating factor that strengthens pelvic floor muscles, making the bladder muscles move and causing contraction of the detrusor muscle and relaxation of the urethral sphincter; thus, urination occurs. Data in our hospital revealed that the pelvic floor muscle strength of patients was greatly strengthened after low-frequency electrical stimulation treatment. In addition, low-frequency electrical stimulation also improved the blood circulation of pelvic tissues (including the bladder and urethra), promoting the healing of surgical trauma. Moreover, pulse current stimulation to the nerve controlling bladder can also accelerate the recovery of nerves controlling the bladder and urethra [21].

There are two mechanisms for the treatment of postoperative nerve injury. One is urinary retention caused by bladder detrusor dysfunction, and the main treatment is to recover the activity of the detrusor. Since the internal sphincter and bladder detrusor are controlled by the sympathetic and parasympathetic nerves and in urine activity, the role of sympathetic nerves is second and the parasympathetic nerve plays a dominant role, while pelvic nerves originate from sacral spinal nerves 2–4, which is rich of parasympathetic fibers, in which excitement can make the detrusor contract and the internal bladder sphincter relax, promoting urination [22, 23]. Therefore, the treatment is as follows: two electrodes are connected to the A1 channel of the neuromuscular stimulation therapy system (Phenix), electrodes are placed in the position of sacral spinal nerve 3, and the bone electrode is attached to the bone; the frequency is set at 35 Hz, pulse width at 200 μs, for 15–30 min each treatment, twice a day, for a duration of 3 days, and then, the catheter is removed. The second treatment is the use of endorphin procedures to relax abdominal and pelvic floor muscles with an analgesic effect [24]. In theory, the latter is suitable for muscle tension caused by pain and infection factors after delivery and general surgery [25], and its treatment program is as follows: electrical stimulation frequency is set at 1 Hz, pulse width is set at 270 μs, for 15–30 min each time, twice a day, for a duration of 3 days, then the catheter is removed. However, data of our hospital suggest that in the preventive treatment for urinary retention after cervical cancer operation, the second method seems to be more effective, and the possible reason may be as follows: even the chances of damage to pelvic floor tissues, blood vessels and nerves are greater in cervical cancer operation than in general gynecological surgery, and postoperative urinary retention caused by muscle tension are still dominant. This may be an important discovery in our clinical work.

The female pelvic floor is composed of multi-layer muscle and fascia, supporting and maintaining the pelvic organs in the normal position, in which the inner pelvic diaphragm is the most tough layer of the bottom of the pelvis, including the levator ani muscle and its fascia. Pelvic floor muscle fibers are divided into two types; most of the type I muscle fibers distributed in the levator ani muscle, and type II fibers are located in the superficial pelvic floor.

The pulse current below 1 000 Hz is called low-frequency electrical stimulation. Biological electrical stimulation is the use of low-frequency electromyography to stimulate neuromuscular stimulation. Through passive muscle training, the nociceptors are awakened to accelerate the regeneration of nerve and the recovery of conduction function, stimulate muscle contraction, improve blood circulation, and increase its contraction strength and elasticity, which can enhance pelvic floor muscle strength.

Therefore, pelvic floor electrical stimulation treatment can effectively improve the pelvic floor electrophysiology to repair the damaged neuromuscular; the patient’s pelvic floor muscle strength was significantly improved. The results of this study further indicate that pelvic electrical stimulation can enhance pelvic floor muscle contractility, which is consistent with other studies reported. All in all, through the pelvic floor electrical stimulation treatment, pelvic muscle contraction can effectively improve the function and promote postoperative pelvic floor muscle strength recovery, thereby enhancing the postoperative quality of life.

There are some shortcomings in this study, including the small number of samples included, and non-multi-center research, which makes it difficult to recruit a sufficient number of representative research objects.

Low frequency electric stimulation is an effective treatment for pelvic floor dysfunction, which has gained attention in recent years, while through observation, we found that it is also significantly effective for urinary retention, non-expensive, non-invasive, easy to operate, its curative effect is not related to age, weight, and so on, and is easily accepted by patients. Thus, it is worthy of clinical promotion. However, low-frequency electrical stimulation treatment for urinary retention after cervical cancer operation remains as a new field of exploration; further assessments of its effect, as well as continuous research and exploration, are required in the future.