ABDOMINAL PAIN IN PORPHYRIA

INTRODUCTION

Abdominal pain experienced by people suffering from porphyria may be one of three things.

• Pain unrelated to porphyria, and benign, e.g. pain caused by constipation, 'winds', irritable bowel, etc.
• An acute attack of porphyria, mild or severe, and potentially dangerous.
• Pain indicating a more serious problem, e.g. appendicitis or a peptic ulcer.

It is important to distinguish these three causes as the treatment is quite different.

WHICH FEATURES ARE CHARACTERISTIC OF PAIN DUE TO PORPHYRIA?

The cardinal feature is that these are attacks—i.e. discrete episodes lasting several days, with complete freedom of symptoms in between. Pain which comes and goes as the day progresses, or chronic pain present day after day, is highly unlikely to represent a true symptom of porphyria. Secondly, patients are, and look, ill.

Read the following page: Acute symptoms in porphyria.

1.  Severe acute attacks

The patient usually experiences the following.

• severe abdominal pain
• which may also be felt as a dragging discomfort in the lower back, loins and legs
• nausea; vomiting is not invariable
• mildly elevated blood pressure and pulse rate
• passage of dark urine
• and, perhaps, paralysis.

2. Mild acute attacks are signified by the following

• abdominal pain as above, lasting continuously for several days,
• continuous throughout most of the day and night,
• accompanied by loss of appetite and possibly nausea.

Today, these milder attacks are more common than classical acute attacks, particularly as patients and their doctors are more aware of porphyria. Very often a cause for it will be evident (e.g. the patient may be taking a drug which is 'not safe' in porphyria).

This highly characteristic pattern of pain must be clearly distinguished from other causes of pain: for instance the frequent, episodic, cramping, chronic nature of spastic colon. Urine ALA, PBG and porphyrins MUST be measured and found to be significantly elevated before the symptoms are ascribed to porphyria.

CONFIRMING THE ACUTE ATTACK AS THE CAUSE OF THE PAIN

It is important to take a good history and examine the patient thoroughly.

The only reliable confirmation of porphyria as the cause of the pain, is the demonstration of elevated aminolaevulinic acid (ALA) & porphobilinogen (PBG) and porphyrins in the urine. People experiencing abdominal pain on the basis of their porphyria will have a very active porphyria metabolically. One usually finds high levels of porphyrins in their urine and the precursors— ALA and PBG— will be raised. This is strong evidence for an incipient acute attack.

Consult the following pages for details: Diagnosing porphyria: patients with suggestive symptoms, Acute symptoms in porphyria

Note that examination of the urine alone is sufficient to gauge whether the VP is active enough to be causing pain. This is in contradistinction to the straightforward diagnosis of VP where a plasma scan result is sufficient. This is because, when the porphyria is more active, one has a much larger amount of porphyrins appearing in the urine and for this purpose, urine estimation is more informative.

MANAGEMENT

It is important to stress that until proven otherwise it must always be assumed that the abdominal pain experienced is due to an incipient acute attack. Such an attack can prove fatal if left untreated. Patients should be instructed to:

• Cease their medication and
• Consult their doctors without delay.

They should, under no circumstances, continue taking medication unless they have been assured by a competent doctor, after proper consideration, that the pain is not due to porphyria.

If the pain is believed to be due to a mild acute attack, with no vomiting

• Medication is stopped
• Urine specimens sent to the laboratory for the determination of ALA, PBG and porphyrins
• The patient is given symptomatic treatment with paracetamol-codeine compound for pain
• And is told to ensure an adequate intake of oral fluids and carbohydrates
• And is carefully monitored to ensure that symptoms settle promptly.

If the patient has symptoms of a more severe attack, is vomiting or fails to improve promptly

• Patient is admitted and managed as described here: Management of the acute attack.

Under no circumstances should the patient take antispasmodics such as hyoscine butylbromide (Buscopan) etc., as this may very well precipitate an acute attack. These measures are usually sufficient for the episode to pass on in 1-2 days.

TWO IMPORTANT CAVEATS

1. Never forget that the abdominal pain of porphyria is not associated with peritonism. The absence of abdominal tenderness, guarding, rigidity or rebound tenderness is typical of acute porphyria, and does not imply that the patient is simulating illness.
   
   
2. Pethidine addiction is almost unheard of among our porphyrics. I am aware of just one patient (whose VP is in fact inactive) in South Africa who manifests true pethidine-seeking behaviour. Characteristic behaviour among many patients is to demand pethidine repeatedly during their admission, often with sudden improvement immediately thereafter, only to cry for pethidine again within a short time. Yet, as soon as the acute attack settles, all demands for pethidine cease and the patients are discharged. This is totally incompatible with any definition of opiate dependence, and proves that the opiate requirement is genuinely in response to pain. Unfortunately many doctors and nurses with no experience of porphyria fail to realise this, and resort too easily to labels such as "pethidine dependence".

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