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Abdominal Pain in Pregnancy

Abdominal Pain in Pregnancy

Stuart B. Blakely, M.D.

Binghamton, N.Y.

Abdominal pain in pregnancy is frequent and has not been thoroughly studied. Few women escape some abdominal discomfort or distress. Eighty-five percent definitely complain of such pain at some time during the nine months, but the literature on the subject is meager. Brief references are scattered through obstetric textbooks. Only two journal articles in English could be found; hence this clinical study of abdominal pain in 300 consecutive private obstetric cases.

Since it is entirely unpractical to attempt to name all the causes of abdominal pain, with or without pregnancy, this paper will deal only with abdominal pain directly caused by. or closely associated with the enlarging uterus or the pregnant state. Pregnancy is, of course, not immune to any of the numerous intra-abdominal and extra-abdominal condition that causes pain in the abdomen, a fact to be most strongly emphasized and ever borne in mind.

Nervous anatomy, detailed differential diagnosis, and therapy are not considered. There can be no discussion of the theory and definition of pain and only a brief reference to the mechanism of the production of abdominal pain. Much abdominal pain in pregnancy is somatic, i.e., arises in the parietes of the abdomen. Mackenzie's theory of the viscerosensory reflex may explain the localization of some true visceral or splanchnic pain. However, the conclusion that pain may be actually felt locally in both solid and hollow viscera seems inescapable. Examples of visceral pain felt locally in the organ involved are the pain of ablatio placentae, of a subserous fibroid under tension, or of a distended and inflamed ureter or kidney pelvis. John Morley has well summarized the differences in the character of visceral and somatic pain: Pure visceral pain is deep-seated, dull and heavy, often intermittent, widely radiating and imperfectly localized; in contrast, pure somatic pain is more superficial, sharp and stabbing, felt over a smaller area, more accurately localized, and at times associated with local tenderness and muscular rigidity. These differences should be remembered during the further development of this paper.

ETIOLOGY OF ABDOMINAL PAIN IN PREGNANCY

True inflammation is not an important etiologic factor. Most abdominal pain in pregnancy is the direct or indirect results of either uterine enlargement or uterine contraction. The uterine enlargement causes pain by its own distention (often with or followed by uterine contraction) or by pull (stretching) or pressure exerted on organs or tissues. The uterine contraction causes pain chiefly by smooth muscle tension, which Hurst believes to be the cause of all true visceral pain. However, it is difficult to explain why one uterine contraction is painful and another not, when the two are of the same apparent intensity and degree of hardness to the examining hand. The pain of both enlargement and muscular contraction of the uterus is augmented by the pain produced in the abdominal wall by these two processes. Disturbances of function (e.g. ureteral dilatation) and interference with the blood supply (e.g.. Degeneration in a subserous fibroid) are at times causative or contributory. Three other conditions must be mentioned in this brief consideration of the etiology of abdominal pain in pregnancy extrauterine gestation, certain types of placental hemorrhage, and "liver" toxemia.

Abdominal pain in pregnancy is frequently without physical signs, is with difficulty described by the patient, and often strangely comes and goes without apparent reason. Generally speaking, its severity is in direct proportion to the rapidity of the development of the cause. An atypical pain occasionally defies analysis; most of these can be traced to their source by study sometimes, it is true, only in retrospection. It is very important to remember that individuals differ markedly in their reaction to painful stimuli and also that many factors in all pain production are still underdetermined.

FACTORS INFLUENCING ABDOMINAL PAIN IN PREGNANCY

Age, Ranging in this series from 17 to 48 years, age alone apparently exerts no influence. Table 1. Complaints of pain by Month of Pregnancy.

First. 5

Second. 19

Third. 22

Fourth. 40

Fifth. 60

Sixth. 65

Seventh. 85

Eighth. 117

Ninth. 65

Table 2. Complaints of Pain and Location in Abdomen

Lower part of abdomen... 341

Central part of abdomen..... 38

Upper part of abdomen......142

The complaints of pain were more than twice as frequent in the lower as compared with the upper part of the abdomen.

Parity, - Primiparas complain slightly more frequently of abdominal pain than multiparas. The latter are rarely able to recall any suffering in a previous pregnancy.

Habitus, - The tall slender asthenic women suffers more from stretching of the lower part of the abdominal wall, while the short stocky asthenic patient with short abdomen from the pubis to the ensiform cartilage tends to have more pain in the upper part of the abdomen. The difference is not marked.

Period of Pregnancy, - The incidence of pain increases with each month up to the ninth and then markedly lessens, there being only slightly more than one-half the number of complaints of pain in the last month as in the eighth. I have no explanation for this apparent contradiction. Practically all pain disappears post-partum, that of the biliary and urinary tracts occasionally excepted.

Time of Day, - Symptoms due to stretching of the lower part of the abdomen and round ligaments are worse at the end of the day. Pain that wakes the patient night is usually colic of a hollow viscus or an intra-abdominal accident.

Regions of the Abdomen, - Pain is more frequent in the lower than the upper part of the abdomen, and in both more on the right side. The lower part of the abdomen is the region of the greatest changes during pregnancy. The location of the appendix and gallbladder on the right, the displacement of the uterus toward that side and the greater activities of the right extremities may partially explain the preponderance of right-sided pain. Early in pregnancy, the pain is almost always low in the abdomen; if central, in the bladder or uterus; if lateral, in the ovary of occasionally in the tube or round ligaments. Later, the pain caused by stretching of the abdominal wall and round ligaments is common. In the last two months, the pain is still chiefly in the lower part of round ligaments is common. In the last two months, the pain is still chiefly in the lower part of the abdomen and is, without question, most frequently of uterine origin.

Table 3, 4 and 5, give the location of the complaints of pain in more detail, the number of complaints in the different areas and comments on the origins of the pain. There is a preponderance of pain on the right side in all.

Scars, - Among the 300 cases there were forty-seven operative scars of varying age, length, and location. In only seven instances was their pain in or near them a finding contrary to common impression.

Position, Exertion and the Like. - Walking or sudden body movement sometimes causes a painful local cramp in the distorted abdominal muscles or round ligaments. Lower abdominal pain caused by stretching these tissues or the pelvic joints is usually increased by the patient being on her feet and is relieved by rest and adequate support. A painful round ligament is not uncommonly stretched and made worse by the patient lying on the opposite side. Pain in the upper part of the abdomen is often made worse by sitting (pressure increased) and made better by standing (pressure lessened). A sudden increase of intra-abdominal pressure may start or aggravate abdominal pain; e.g., by coughing, sneezing, vomiting or the like. Jolting and jarring at times make worse the symptoms of an ectopic gestation or a "pyelitic." Weak feet, faulty shoes, relaxed Sarco-iliac joints, disturbances of equilibrium and changes of stress and strain in the back an abdomen are undoubtedly definite though often obscure factors in the production of abdominal pain in pregnancy.

Position and Presentation of Fetus, - In vertex presentations the side on which the buttocks are seems to be slightly more frequently the site of pain. Distress in the upper part of the abdomen is common with a breach.

Intra-Abdominal Conditions, - Previous pelvic or abdominal peritonitis does not particularly predispose to pain in a subsequent pregnancy if the inflammatory process has ceased. Adhesions in and of themselves are without symptoms unless by the action of the uterus they are made in some way to interfere with function. Some painful intra-abdominal conditions may be improved by or during pregnancy; e.g., abdominal hernia, visceroptosis, gastric ulcer. In general, however, the pregnant abdomen seems to be more prone to painful sensations than nonpregnant. Some preexisting intra-abdominal conditions are frequently worse; e.g., inflammatory processes, stasis or obstruction of the intestinal and upper urinary tract, disease of the liver and bile passages, and abdominal carcinoma.

CLASSIFICATIONS OF ABDOMINAL PAIN IN PREGNANCY

A satisfactory classification of abdominal pain in pregnancy is difficult. Possibly, excepting colic, muscle spasm, sudden rending of tissue and sudden peritoneal insult, the average patient's characterization of pain is not clear and is of questionable value. For this reason, little description of pain has been attempted.

The anatomic origin of abdominal pain in pregnancy may be grouped as follows:

Abdominal parietes.

Uterus, its contents and adnexa.

Extragenital locations intestine, liver with bile passages, and urinary tract.

It is probably simplest and best to consider in order pain originating in these locations, at the same time discussing the mechanism of its production, and the location of the pain as felt by the patient.

PAIN ARISING IN THE ABDOMINAL PARIETES

The term abdominal parietes include not only the anterior and lateral abdominal muscles with their facial coverings, extensions and insertions, the subperitoneal tissue and the parietal peritoneum, but also the pelvic girdle, the lower part of the thoracic cage, and the pelvic and costal diaphragms.

The posterior wall of the abdomen is not, strangely enough, a proved source of pain in pregnancy. It is entirely possible that some ill-defined abdominal pain may be a true referred pain from the posterior wall. A lower lateral abdominal pain, relieved by lying on the side with the thigh sharply flexed, has suggested psoas muscle origin.

Stretching of the skin and fat of the anterior and lateral abdominal wall does not cause actual pain, nor does the thickness of the wall seem to be an important factor. Short, Sharp, scattered, stabbing pains in the lower part of the abdomen suggest and only suggest stretching of the subperitoneal tissue. Indefinite, ill-defined, more or less general lower abdominal pain may be due to stretching of the wall or round ligaments (if early), but I believe it is more commonly of either large intestinal or uterine origin especially the latter. Generally speaking, pain caused by stretching of or pressure on the lower abdominal wall is felt most commonly along broadband curving from one anterosuperior spine down over Poupart's ligaments and the pubis to the opposite spine. The patient will often outline this pain by moving her hands up and down along this area or by putting her hands in a position as if to support the abdominal wall in this region. The painful sensations are sometimes complained of as being sharper over the centers of Poupart's ligaments (insertion of the round ligaments) and over the pubis and pubic spines (insertions of Poupart's ligaments and the rectus muscles). These pains are not in evidence in early pregnancy, are very variable in character and appearance irrespective of the tenseness of the wall and are influenced by factors already mentioned.

The region of the pubis may be painful by direct pressure of the fetal head or by stretching of the rectus insertions and the pelvic girdle. A low, central more or less vertical pain above the pubis, indicated at times by a typical up and down movement of the patient's hand and fingers, seems to be associated with relaxation of the symphysis pubis, often with demonstrable tenderness, even separation, of the joint as well as tenderness of sacroiliac joints. Rarely, sudden "lightning" may cause lower abdominal pain. Stretching of the pelvic diaphragm in the later months sometimes results in a sharp pain shooting from the pelvis or vagina up through the lower part of the abdomen.

An abdominal hernia may be painful by stretching of the ring or by a pull on adherent contents, hernias are "cleared" by the rising uterus and give no symptoms. The larger the hernia, the farther from the midline and the higher in the abdomen, the less likely is this "clearing" to take place. In a few instances, I believe that I have observed pain due to stretching of the tissues about the navel.

In the upper part of the abdomen, in the later months, is the discomfort, occasionally amounting to pain, caused by stretching of and pressure on the lower thoracic cage (including rib margins with rectus insertions) and on the diaphragm, which is at times felt in the back at the level of the insertion of the diaphragm, fairly common is the painful "slipping" of the (usually) seventh or eighth costal cartilage with definitely localized tenderness. As always, pain in the upper part of the abdomen may present many diagnostic difficulties.

PAIN ORIGINATING IN THE UTERUS AND ADNEXA

Two types of pain originate in the uterus; local and diffuse.

The local type, sharp, sudden, usually well localized, is caused by tension or tearing of uterine tissue or in a fibroid. It is often accompanied or followed by the diffuse type.

Diffuse uterine pain is caused by uterine distention and (or) contraction (the latter with an element of colic) and is felt in the lower part of the abdomen between the pubis and the navel, an area connected with the eleventh and twelfth segments of the dorsal cord. Occasionally, diffuse uterine pain is felt above the level of the navel or in the anterior thighs and has been explained on the basis of an anomalous nerve distribution or supply. However, I am not at all sure that diffuse uterine pain is a Mackenzie viscerosensory reflex. The patient usually indicates its site by drawing her hand more or less horizontally across, though not entirely across, the lower part of the abdomen, or by drawing both hands, in the same manner, a little lower nearer the pubis. The diffuse type of uterine pain is intermittent (though in early abortions apparently almost continuous), often begins at night, is accompanied by sacral pain and hardening of the uterus, is not relieved but usually made worse by enemas, and is often followed or associated with vaginal discharge.

Uterine contraction is by far the more frequent cause of the diffuse type of uterine pain, threatening or presaging abortion if early, labor if late. Here belong the "false" or "wild" pains. Rapid stretching of the uterine musculature produces the same type of pain without the element of colic (though this is often added or superimposed), as in acute hydramnios, accidental hemorrhage, and infected uterine contents. In this category is the incarcerated uterus with bladder distress. Any acute uterine distention may also exhibit pressure symptoms on the wall or contents of the abdomen. Abruptio placentae usually present a sudden sharp, more or less severe local pain due to tearing of the tissue, followed by diffuse pain. The same occurs with hemorrhage in a hydatidiform mole, though usually earlier in pregnancy. Rupture of the uterus gives the pain of muscle tearing, followed by that of peritoneal irritation due to escaped blood and uterine contents. If the rupture is rapid, extensive and in the upper part of the uterus, the peritoneal signs may be most marked in the upper part of the abdomen with shoulder pain. If the placenta lies under the point of rupture, all symptoms are frequently less severe. Abdominal pregnancy is usually quite painful because of more direct undamped fetal trauma. Fetal movements are occasionally painful, even in a normal pregnancy, especially in a tense uterus or when they impinge on a tender tissue or organ.

Fibromyomas in the pregnant uterus, even when large and multiple, are frequently without symptoms. They may cause pain by torsion of a pedicle, by tension in a fibroid (usually subserous) owing to circulatory, degenerative and even infective changes. This last cause (tension in a fibroid) is the most common cause of abdominal pain in pregnancy associated with uterine fibroids and is usually well localized by the patient. The prominence, tenderness, and pain of the tumor are increased by or with uterine contractions (cause or effect ?). Small fibroids of this type, or small intramuscular or subserous hemorrhages are, I believe, the most common cause of local pain and tenderness in the pregnant uterus. More or less continuous local uterine pain or painful uterine continuous over a considerable period of time without the onset of labor are produced in many cases by the efforts of the uterine musculature to expel small fibroids from its midst. A previous explanation has been "faulty uterine innervation."

The round ligaments might well be considered in many respects a part of the anterior abdominal wall. Pain by their stretching or contractions is common in the lower part of the abdomen from the tenth to the thirtieth week and is felt for a shorter or longer distance along their course from the middle of Poupart's ligaments to the angels of the uterus, though rarely if ever felt above the level of the navel. The ligaments or portions of them can often be felt as tender cords, and the patient usually indicates very accurately their location at least the painful segments. Here belongs the ligament pain associated at times with a previous suspension.

Salpingitis is rare in pregnancy, and I have not definitely observed pain from that source. Varicose veins of the broad ligaments are said to cause pain; their diagnosis must be difficult. Ectopic gestation exhibits abdominal pain that may vary greatly in location, degree, character, and order of appearance; e.g., the low unilateral pain of tubal distention and colic (the tube is stated to be connected with the twelfth dorsal spinal segment), often accompanied by the diffuse type of uterine pain; the local pain of slow rupture of the tubal wall and the effusion of blood into the pelvic tissue or the pelvic peritoneum; the sudden pain of tubal rupture or tubal abortion that "doubles the patient up" (visceromotor reflex?); the diffuse pain of peritoneal irritation. Much depends on the rapidity of the development of the cause.

Pain arising in the ovary during early pregnancy seems to be due to distention of the capsule by the formation of the corpus luteum with more or less hemorrhage, apparently intensified by the presence of "adhesions" and traction by the rising uterus. The pain of ovarian origin later in pregnancy is most commonly associated with the twisting of the pedicle an (or) inflammation of some type of ovarian tumor the word tumor being used here in the broadest sense. Then follows a more or less definite series of pathologic changes accompanied by various sorts of pain. Though the ovary is said to be connected with the tenth dorsal cord segment, the pain in the few cases of the twisted ovarian pedicle that I have seen appeared to be lower in the abdomen than the level to which the tenth dorsal segment is usually assigned.

PAIN ORIGINATING IN THE INTESTINAL TRACT

Occasionally, pain in the right or left upper quadrants, across the upper part of the abdomen or along the course of the descending and sigmoid colon is relieved by the passing of gas or by "unloading" the bowl. A laxative or an enema is sometimes a valuable diagnostic aid. However, real abdominal pain from flatulence or constipation is not so frequent as has been stated. This raises the question of the localization of pain of the large intestine. Hurst believes that pain arising in the more movable portions is felt as diffuse pain in the lower part of the abdomen. Transverse pain across the abdomen above the navel, frequently with or follow by painful uterine contractions, threatening the continuation of the pregnancy. In the three hundred cases studied there were only in which there was evidence of mechanical obstruction of the small intestine. The causes of their symptoms were definitely determined, for they did not come to operation. It is possible that some indefinite central abdominal pain in pregnancy originates in the small bowel. Pregnancy tends to increase intestinal stasis, or any intestinal obstruction, whether from intrinsic or extrinsic causes. The usual explanation is that the symptoms are produced by pressure on or angulation of the portion or portions of the intestine in question, influenced by increased vascularity and by the presence of adhesions and pelvic tumor. Definite symptoms of intestinal obstruction should never be ascribed to pregnancy alone.

PAIN ORIGINATING IN THE LIVER AND BILIARY TRACT

Any preexisting pathologic condition in the liver and biliary tract is almost always worse during pregnancy. Three conditions, induced by pregnancy and frequently associated may produce pain in this sensitive organ group: Trauma by the pressure of the uterus, or fetal part, or fetal movement in the upper portion of the abdomen and epigastrium. Changes in the liver, gallbladder and bile tracts due to increased absorption of toxic and infectious material from the intestinal tract. The conditions mentioned in 1 and 2 present no special diagnostic difficulties peculiar to pregnancy. "Liver" toxemia, so called, especially if acute and in late pregnancy. The pain, more or less continuous, is often very sharp and severe, usually centering in the epigastrium. The mechanism of the liver capsule by hemorrhage or necrosis in the liver parenchyma(?).

PAIN ORIGINATING IN THE URINARY TRACT

The bladder and pelvic ureters are rarely the sources of any pain during pregnancy. On the other hand, the abdominal ureters and the renal pelvis are quite commonly the sites of changes often on a preexisting base which gives rise to pain and other symptoms loosely and carelessly termed "pyelitic of pregnancy". Stasis and infection are the two prime causative factors. The stasis is due to two phenomena peculiar to pregnancy: (1) pressure of the uterus on the relaxed ureters lying on the bellies of the psoas muscles, whether they have been displaced by the uterus as early as the eighth months in 80 percent of pregnancies; (2) hypotonicity of the ureters and renal pelvis, probably caused by some specific substance elaborated during pregnancy. These hypotonic changes are 100 percent in evidence by the fifth months, increasing as pregnancy advances, 83 percent in both ureters, 15 percent in the right one alone, and 2 percent in the left alone. Bacteriuria is present in a considerable number of pregnant women. In most patients, the stasis exists with few or no symptoms, as does the infection. It is impossible to state with any degree of certainty just what extra factor or factors initiate pain in a given case. It seems fairly clear that it is produced by the tension of smooth muscle or an encapsulated organ (ureter, renal pelvis, kidney) by an obstruction, or infection, or both. The pain is rarely colicky but rather continuous with exacerbations. The patient indicates ureteral or radiating (?) renal pain by moving the hand from the region of the public spine outward and upward, parallel with Poupart's ligament, to near the anterosuperior spine of that side, and then curving back into the loin, more often on the right than on the left side. Occasionally, she passes the hand downward in the reverse direction. It may be at times difficult to distinguish this pain from that originating in the large bowel, round ligaments or abdominal wall; but the typical movements of the patient's hand and other symptoms usually make the situation clear.

Even marked pathologic changes in the renal pelvis and kidneys may cause no abdominal pain. When such pain does occur, it is usually indicated by the patient at some point in an area of moderate width extending from about the level of the navel (tenth dorsal segment) outward to just below the rib margin, and thence lateral and posterior into the loin. The diagnosis of a "pyelitic of pregnancy" should never rest on the evidence of abdominal or other pain alone.

SUMMARY OF ABDOMINAL PAIN IN PREGNANCY

Abdominal pain in pregnancy may be classified as to the anatomic origin, mechanism of production and location as felt by the patient. The anatomic organs may be grouped into (1) abdominal parietes, (2) uterus with contents and adnexa, and (3) extragenital organs and tissues.

The pain may be of somatic or visceral origins and is caused chiefly by distention enlargement or contraction of the uterus its source can usually be determined.

Eighty-five percent of pregnant women complain of definite abdominal pain at some period.

The incidence of pain increases with each month up to the last at which time there occurs a marked decrease.

There is more pain in the lower than in the upper part of the abdomen and in the both more on the right side. Abdominal pain pregnancy varies much in character a severity is not immune to any of the causes of abdominal pain.

CONCLUSION Sir James Mackenzie said that pain is the most important of complaints and the most instructive diagnostic sign. Knowledge of pain is scanty; exact information is largely lacking; an investigation is a difficult interpretation of observations is uncertain, and the subject is worthy of study. These words apply also to abdominal pain in pregnancy, a subject to which this clinical study is submitted as a modest contribution. 123 Murray Street

Originally published: Thursday, June 07, 2018; most-recently modified: Monday, May 13, 2019

 

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