Differential Diagnosis Descriptions
Abductor Muscle Sprain (Groin Pull)
- Quality: sharp to burning with any movement, some mild residual pain at rest
- Region: proximal medial thigh to anterior pelvic
- Severity: 8 out of 10 with walking, less severe with rest
- Timing: occurs after strain of muscle, e.g. kicking a ball, resolves over days to weeks
Ilioinguinal Nerve Entrapment
- Quality: burning to dull, may have increased sensitivity or loss of sensation over area involved
- Region: anterior pelvic, low abdomen, radiating into labia majora, may have sensitivity over inguinal canal medial and below the ASIS
- Severity: 8 out of 10, worse after movement, hip extension
- Timing: worsens over time, may be most painful at night
Pelvic Inflammatory Disease
- Quality: dull to sharp
- Region: low abdomen, low back
- Severity: 6 out of 10, worse with sexual activity
- Timing: waxing and waning
Rectus Abdominis Sprain
- Quality: sharp to dull, some burning-aching at rest
- Region: low abdomen
- Severity: 8 out of 10 with abdominal contraction, less severe with rest
- Timing: worsening over days and ultimately resolving
Symphysis Pubis Laxity
- Quality: sharp to dull, some burning-aching at rest
- Region: anterior pelvic, low abdomen
- Severity: 8 out of 10 to 10 out of 10 with walking, less severe with rest
- Timing: mid to late pregnancy, worsening over days to weeks
Urinary Tract Infection
- Quality: dull, burning-sharp pain with urination
- Region: low-abdomen, or ureter with urination
- Severity: 8 out of 10 to 10 out of 10 with urination, less severe with rest
- Timing: worsening over hours to days
Pain Anatomy and Pathophysiology
Symphysis Pubis Overview
The symphysis pubis is comprised of two bones that each has a hyaline cartilage-lined surface, connected by a fibrous disc. A simple graphic design illustrated that the symphysis pubis is comprised of two bones and each has a hyaline cartilage-lined surface, connected by a fibrous disc.
There is no ‘synovial’ joint in this location.
Radiologic Correlates
A coronal MRI section illustrates the position of the symphysis pubis just below the bladder. Expanded inset view illustrates the fibrous disc situated between the bones anteriorly at the midline. The symphysis pubis of this overweight 56-year-old female demonstrates features of degenerative joint disease including osseus hypertrophy, edema, and endplate sclerosis.
Pain Innervation
The innervation of the joint is variously described as coming from the pudendal and genitofemoral nerves (Gamble et al. 1986) and branches of the iliohypogastric, ilioinguinal and pudendal nerves (Standring, 2008). However, no further information is provided regarding the pattern the innervation or which branches supply specific parts of the joint.
Mechanisms
- When inflamed, the joint secretes inflammatory mediators, e.g. serotonin, bradykinin, CGRP, protons, and norepinephrine.
- The peripheral nerve afferent terminations that supply this area have receptors for these mediators and this is part of the pain signaling cascade.
- In the context of inflammation, pain signaling is enhanced.
Pain Pathways
Simplified overview of the pain pathways
The nociceptive signal enters the CNS via the primary afferent nociceiptor. From there nociceptive signals can ascend via synapses in the superficial dorsal horn, Rexed laminae I and II (substantia gelatinosa). The primary signal then ascends via multiple pathways to rostral anterior cingulate cortex (impacting mood and behavior) and S1 cortex (mediating intensity and qualitative features) via the thalamus.
There are other projections but this is a simplified description. Descending modulatory signals project from S1 and other cortical areas to the periaquaductal gray (affecting level of consciousness and sleep) and to the nucleus raphe magnocellularis where facilitation and suppression of pain can occur via descending projections to the dorsal horn.
Once nociceptive signals enter the dorsal horn, spinal cord reflex pathways activate, such as the direct connections to motor neurons which can prompt muscle spasm and protective movements.
Test Your Knowledge: Pain Anatomy and Pathophysiology
All of the following are implicated in inflammatory pain signaling EXCEPT:
Impact of Opioids
Introduction
Consider our Ava, who is still experiencing anterior pelvic pain. This time, however, you learn some additional information reviewing her chart:
- Patient tested positive for opioids at a screening exam early in pregnancy.
Her obstetrician learned from the medical chart that she has been using Percocet to help her ‘relax’ and when her chronic knee pain flairs.
Opioid Dependence and Pregnancy
The American College of Obstetrics and Gynecology (ACOG) has issued guidance on opioid dependence and pregnancy. ACOG has noted that opioid tapering is not recommended for addicted patients during pregnancy as relapse is likely and places the fetus at risk of complications including fetal demise. Support of an addiction specialist is recommended.
ACOG notes that management of delivery pain in the opioid dependent patient generally requires higher doses of opioids when opioids are indicated and adjustment of dosing should be anticipated.
Opioid Pharmacobiology Definitions
- Tolerance: decreased drug effect with a fixed dose.
- Physical dependence: adaptation to a substance manifested by characteristic symptoms when dosage lowered or stopped, or an antagonist is given.
- Withdrawal: signs or symptoms after abrupt reduction or discontinuation of agonist or after antagonist administration.
Opioid Behaviors Definitions
- Misuse: use of a prescribed medication in a manner other than that prescribed, e.g. increased doses, or for another condition.
- Abuse: use of legal drugs inappropriately, or the use of illegal drugs (National Institute on Drug Abuse Definition)
- Chemical coping: use to “cope with emotional stress characterized by inappropriate and/or excessive use
- Addiction: a chronic condition with craving and compulsion but lacking concern and control. (Otherwise known as the ‘6 C’s definition.’)
References
Denisco RA, Chandler RK, Compton WM. Addressing the intersecting problems of opioid misuse and chronic pain treatment. Exp Clin Psychopharmacol. 2008; 16:417-428.
Adapted from https://www.drugabuse.gov/publications/media-guide/science-drug-abuse-addictionbasics
Kwon JH, Hui D, Bruera E. A Pilot Study To Define Chemical Coping in Cancer Patients Using the Delphi Method. J Palliat Med. 2015; 18:703-706.
Opioid Scenarios
Scenario 1
The patient was adamant that she takes ‘Percocet’ only once or twice a month. She’s been using pills left over from a prescription given to her after a surgical procedure about a year ago. The obstetrician counseled her about using opioids and referred her to an addiction specialist for further assessment and treatment.
Scenario 1: Solution
The addictionologist confirmed that the patient’s pattern of drug use was occasional and chronic daily opioid treatment was not recommended but that a short course of psychological substance abuse therapy was recommended. The patient herself advises you of this history. How do you think this impacts the treatment choices?
Scenario 2
The patient was actually taking several doses of prescription opioid daily. She started taking prescription pain pills after a surgical procedure several years ago. Over time, the amount of opioid (in terms of daily morphine equivalents) increased to the point where she now takes 80mg ‘morphine equivalents’ daily.
The obstetrician was concerned about opioid misuse and referred her to an addiction specialist for treatment.
Scenario 2: Solution
The addictionologist confirmed that the patient’s pattern of drug use was consistent with opioid dependence and addiction. Chronic daily opioid dependence treatment was initiated and supportive psychological substance abuse therapy was recommended.
The patient advises you that she is treated with buprenorphine but does not disclose the full history, which you learn from the records obtained. How does this impact the treatment choices?
Test Your Knowledge: Impact of Opioids
True or false? Opioid tapering is recommended for addicted patients during pregnancy?
Assessment of Pain
To assess pain, complete the following questionnaire with the patient:
- Quality
- Region
- Severity
- Timing
- Usually associated with: (fill in blank)
- Very much better with: (fill in blank)
- Worse with: (fill in blank)
Quality
Descriptive feature(s) of pain Essential for clinical assessment
Can include descriptions like:
- Tingling
- Painful
- Burning
- Stinging
- Deep
- Prickling
- Throbbing
- Dull
- Time
- Seconds
- Tolerable
- Aching
- Pain
- Numbness
- Progressive
- Hand
- Like
- Numbing
- Radiating
- Intense
- Uncomfortable
- Sharp
Region
- Localization of pain
- Essential for clinical decision making
Severity
People vary tremendously in pain perception. Highly personal intensity valuation is normal.
The majority of people rate their pain at a 5, with the next most popular pain score reported tied between 6 and 7. The third most reported pain value is 4, then 3, then 8, then 2, then 9, then a tie between 1 and 10, and finally 0 being reported the least often.
Timing
The tempo of pain tells us a lot about potential causes and prognosis. Both daily and longer-term variations can be important.
Assessment Can Make a Diagnosis Possible
- Quality
- MI: Crushing, Costochondritis: Sharp
- Region
- MI: Sub-sternal, Costochondritis: Peri-sternal
- Severity
- MI: Varies: 7 to 10, Costochondritis: Varies: 4 to 10
- Timing
- MI: New onset, worsening, Costochondritis: Waxes and wanes
- Usually associated with
- MI: Diaphoresis, SOB, Costochondritis: Exercise
- Very much better with
- MI: Catheterization, Costochondritis: NSAIDS, ice
- Worse with
- MI: Exertion, Costochondritis: pressure reproduces the pain
Types of Pain
Nociceptive
‘Normal’ pain sensing in response to threats in the environment
Inflammatory
Heightened pain sensing that increases sensitivity to normal levels of touch, pressure, and position
Neuropathic
Aberrant signaling in response to stimuli that increases pain perceived in response to non-painful and painful stimuli
Pain Types Comparison
Nociceptive
Specifics of mechanism
- Activation of nociceptive afferents using ordinary mechanisms of sensing
- Examples: pricks, burns, cuts, blows, breaks, crushes, chemical exposures
Inflammatory
Specifics of mechanism
- Activation of afferents following modification in response to inflammatory mediators
- Examples: arthritis, inflammation, infection
Neuropathic
Specifics of mechanism
- Activation of nociceptive processing pathways due to disease or dysfunction of nervous system
- Examples: neuropathy, MS, transverse myelitis, spinal cord injury, nerve damage
Treatment Based on Pain Type
Nociceptive
- Non-pharmacological treatment: cold or cooling, rubbing (counter irritant), disctraction
- Pharmacological treatments: NSAIDs, local anesthetics, opioids (severe and acute)
Inflammatory
- Non-pharmacological treatment: warmth (heating pad, Epsom salts), or cooling, gentle exercise, PT: strengthening, stretching, bracing
- Pharmacological treatment: NSAIDs, acetaminophen (non-antiinflammatory), disease modifiers, minimize opioid use
Neuropathic
- Non-pharmacological treatment: distraction, self-management, CBT/ACT, PTC, empathetic support
- Pharmacological treatment: pain-active antidepressants, pain-active anticonvulsants, local anesthetics, minimize opioid use
Chronic Pain Pharmacology
How to Design a Pharmacological regimen
Chronic pain is often addressed with more than one medication. The choice of medications is ideally based on evidence that the medication is effective against a particular condition. In the event that a firm diagnosis is not yet established, or that there is no published evidence specifically pertaining to a condition, or that a condition does not respond adequately to the established treatments, it is necessary to tailor a regimen to improve patient outcomes.
The principles of rational pharmacotherapy are represented figuratively in this image description. In the diagram, there is an overlapping series of bubbles in a Venn diagram. The bubbles include NSAIDs/acetaminophen, neuromodulating medications: anti-depressants, neuromodulating medications: gabapentinoids, opioids (a much smaller bubble), and topical agents. Depending on the type of pain (mechanism-based classification of pain) that a patient presents with, the provider will recommend a different set of medications be incorporated into the treatment regimen.
Inflammatory Chronic Pain
Pharmacology overlaps mostly between NSAIDs/acetaminophen, topicals, and neuromodulating: anti-depressants. Pharmacology shares smaller overlaps with neuromodulating: gabapentinoids and to a far lesser degree, opioids.
Nociceptive Chronic Pain
Pharmacology overlaps mostly between NSAIDs/acetaminophen, topicals, neuromodulating: anti-depressants, neuromodulating: gabapentinoids and to a far lesser degree opioids.
Neuropathic
Pharmacology overlaps mostly with neuromodulating: anti-depressants and neuromodulating: gabapentinoids. Lesser overlaps include topicals, NSAIDs/acetaminophen, and to a far lesser degree opioids.
Opioids must be reserved for chronic pain conditions that: 1) have well established pathophysiology, 2) clearly are known to respond to opioids, and 3) in patients for whom the opioid risk profile is established as very low and 4) who are compliant with a structured monitoring program.
Comprehensive Pain Treatment
Multimodal Approaches
The following all contribute to treating pain:
- Physical therapy: conditioning
- Psychological support: skillful living
- Acupuncture, massage: natural defenses
- Sleep, ‘tune-up’: restoration
- Interventional care: ‘rescue’
- ‘Neuro-active’ medications: pain modulation
- Ergonomic adaptation: productivity
- Standard analgesia/OTC meds: temporary relief
Types of Medications
NSAIDs and Steroids
- Medication names (examples): Ibuprofen, Naproxen, Etodolac, Ketorolac, etc.
- Utilization summary: Work well for inflammatory pain but also good for mild to moderate nociceptive pain.
- Major cautions: NSAIDs: GI bleeding, renal.
- Steroids: not for long-term use Typical use: As needed and limited courses
Neuro-active: Anti-Depressants
- Medication names (examples): Nortriptyline, amitriptyline; venlafaxine, duloxetine, etc.
- Utilization summary: Take time to start working, but quite effective and generally safe for long-term use.
- Major cautions: Some may increase suicide risk, need to monitor use. Typical use: Must take daily for drug to work.
Neuro-active
- Anti-convulsants Medication names (examples): Gabapentin, pregabalin, carbamazepine, topiramate, etc.
- Utilization summary: Work especially well for neuropathic (nerve) pain, work well together with other agents.
- Major cautions: may increase dizziness, impair thinking. Typical use: Recommended for daily dosing.
Opioids
- Medication names (examples): Morphine, oxycodone, codeine, Fentanyl, etc.
- Utilization summary: Work well for short periods, but effect wears off quickly and potency declines with use.
- Major cautions: Potentially dangerous: many deaths each year.
- Typical use: Not ideal for daily use.
Neuro-active: others
- Medication names (examples): Lidocaine, acetaminophen, tramadol, muscle relaxants.
- Utilization summary: Work through various pathways, often used alone or in combination with other medications.
- Major cautions: Side effects vary but should be reported if suspected. Typical use: Dosing varies with drug.
Active Strategies
- Tailored exercise
- Daily stretching
- Core exercises
- Yoga
- Meditation
Freely Available Review Articles
(BABB 2010) Treating pain during pregnancy: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2809170/
(Becker 2010) The adult human pubic symphysis: a systematic review: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3035856/
(Elden 2016) Predictors and consequences of long-term pregnancy-related pelvic girdle pain: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4941027/
(Fagevik Olsen 2009) Self-administered tests as a screening procedure for pregnancy-related pelvic girdle pain: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2899498/
(Flack 2015) Adherence, tolerance and effectiveness of two different pelvic support belts as a treatment for pregnancy-related symphyseal pain: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4339641/
(Kanakaris 2011) Pregnancy-related pelvic girdle pain: an update: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3050758/
